Fate says that you keep everything out in the open. Even that hidden aspect itself. Players are expected to keep their knowledge apart from their characters and play as such.
If a character takes a shot at discovering the truth, then it's a contest like "empathy vs. deceive" like you described. Per the principles of Fate, every game mechanic should be out in the open as usual, including but not limited to rolls, results, fate point expenditure, aspect and stunt invocations etc. It's the result that makes the difference.
Success means the character gets the upper hand, just like the player expected. Failure however, is the interesting part. Since in a contest, one side's failure is the other one's success, you can set the roll with opposed goals, like the PC trying to create an aspect like "I know what you did last summer", and the NPC trying to even deepen the deception by creating another aspect like "The sweet taste of false hope".
Aspects in Fate are a more versatile tool than you'd expect at first sight. Don't forget that every aspect is a piece of the truth about yur game world. Even when they don't provide game-mechanical bonuses, they still impose themselves on the story. If there is an aspect that implies that it's not public knowledge, something like "Accountant by day, axe murderer by night", it means that most people, including the PC's don't know about it unless some other aspect says otherwise.
Don't get me wrong, the players can and should know about all aspects in play. It's their character who doesn't know. If a player makes his character act as if they know, feel free to ask them how?. If they cannot find or create an aspect that justifies their knowledge, then you can safely say that they do not know it yet, so can't act on it now.
Fate is a different system than most of the classic games we have played. It offers loads of fun if you embrace the thinking behind it and play along :)
Extras can do anything.
(The price of doing anything is that you have to tell people about it in advance.)
Everything you pulled from the back issues of the Fate Codex is best understood as an optional Extra. It isn't something you're suddenly deciding certain Aspects can do, something you'd suddenly drop into your campaign after everyone's already made and played their characters; it's something you'd bring in at session 0 so people knew you were thinking about it when they did character creation.
Extras are, basically, house rules. Is there any limit to what an Extra can do to an Aspect? Can it get a stress track, consequences, its own high concept and trouble? Can it provide passive bonuses? If the Extra says so, sure. Maybe the only limitation on what can happen is the essential nature of Aspects - that they represent true things about the world fiction.
(Yes, even if the Aspect is a lie. Yes, even if it's "Viscount Poncingjay was abducted by bears!", quotes included. The true thing the Aspect represents is that someone believes that lie.)
But "when you're writing house rules you can write whatever you want and the universe won't explode" isn't a very helpful answer, so I'll do my best to be more specifically helpful, talking about some of the principles behind the Extras you found.
"Succeed without rolling" - the simplest Extra
There are two circumstances where an Aspect can let you succeed without rolling, and they're a little different in terms of how much Extra needs to be done with them.
One is no extra at all, what's defined in the rules as Declaring a Story Detail - in the most general form this is spending a fate point to convince the GM to bend the story in your favor, but because it often involves an Aspect you have, you can think of it as being the opposite of a compel -- spending a Fate Point on one of your own Aspects to get you into dramatic uncertainty from a hopeless position, or through dramatic uncertainty to a favorable resolution.
The other is something you've described under "Always True" - writing one of your Aspects in a way to exempt you from certain dramatic rolls without spending Fate Points. Say, if you're playing a sendup of 90s kids' tv about a bunch of kids on bikes, and one person wants to play Artie, the Strongest Man in the World, because kids on bikes can get up to a lot more mischief when the Strongest Man in the World helps out now and again. As an Extra, everyone comes to an agreement that because of this Aspect, Artie doesn't have to roll to do anything that would be a dramatic feat of Physique and Athletics for a kid on a bike, but can roll to perform dramatic feats of Physique and Athletics no kid on a bike could dream of.
Taking the time to establish an Extra and come to an agreement about who gets to skip out of rolls and how is far better than just, what, expecting the GM will agree with you that you can just get out of a scene they intended to put you in? There may still be some story detail-level spackling that you need to do around the edges, but if you want the broader world to treat you differently, it's Extra time.
Aspects informing Stress tracks
So, something that happens every now and again is that somebody decides to make an Aspect-only version of Fate, where everybody has about ten Aspects split between various categories, and instead of having any skills at all, when you have to make a dramatic roll you add the number of your aspects that apply to it. "The total number of Aspects that apply" can be an interesting concept, but why apply it to a stress track?
Well, the game's existing stress tracks depend on some skills that don't see a lot of play in their respective arenas, where there are several other skills that generally rack stress on opponents. If you're introducing an entirely new stress bar, unless there's an entirely new set of relevant skills you can pick a "stress skill" from, going to some other determiner makes sense. Some kind of world-fiction based determiner, like your total count of relevant Aspects.
Now, in both those cases, because you're looking at the world fiction, Aspects as dual-sided elements of your character represent the tension in the fiction that answers the question "why doesn't everybody just have all the money/magic?"
In the space scum & villainy case, using Aspects about the pricey things you own to determine your Wealth stress track reflects a common tension among scoundrels: is enjoying the comforts of wealth worth the responsibility of wealth maintenance? Sure, you've got Glitterstar, My Shining Piece of Bigshot Station but you've actually got to deal with the ins and outs of running a casino, and all the up-and-coming rogues out to get your piece away from you, and maybe you can trust somebody to run the place but can you really trust them? It gets in the way of chasing down leads to big scores, free as a starbird.
In the mage case, the tension is: you can master magic, but at the cost of cutting yourself off from the mundane world. Having a lot of magic-relevant Aspects means you won't have many relevant to social interaction or physical confrontation, and one use of a compel is to pull you into a situation where you're not very strong.
Consumable "Ammo" Aspects
Can an Aspect have a stress track, and when the track fills the Aspect goes away? Can an Aspect be consumed? Lots of Aspects, usually Create an Advantage stuff, go away when they don't make sense in the world fiction anymore. And if an Aspect represents something consumable, like Extra Ammo, then when it's consumed in the world fiction (at an appropriate level of abstraction, like "clear out a gun stress") it goes away.
Gear Aspects
These are the only type of Extra you might introduce in the middle of a campaign, and as a result they should have a less comprehensive scope than the game-wide Extras you introduce in the beginning. This is the case for both special Gear Aspects in the Fate Core extras chapter.
There's actually nothing extra at all about Brace Jovanovich's Dueling Pistol, from a certain perspective. You spend a refresh to get what is by all appearances a standard conditional +2 stunt. There's a little documentation on how you might get compelled by it, but nothing unusual.
Demonbane, The Enchanted Sword is basically putting itself halfway between story detail and actual Extra, detailing a few specific dramatic things it will automatically succeed at... if you spend a Fate Point on its aspect.
Best Answer
Brute forcing is going to be solved by application of two principles.
Neither of them are totally rules-oriented. The rules aren't interested in stopping brute-forcing, because sometimes it's fun: you're in a contest, you need to get through that door before someone finds you, and it might be fun to just kick it in several times until it smashes into splinters.
Both are going to involve the narrative instead. I'm going to assume you get that Fate's a narrative game, that when they roll, it's because they're doing something in-game that initiates a roll.
1. Failure should produce interesting results.
You might know most or all of this, but I'll go into this anyway in case you don't or for the readers that don't. This one principle alone won't fix it but sometimes it'll help a lot.
Fate suggests dice should only be rolled when failure would be interesting, or alternately might be achievable at an interesting cost:
That's often going to force a change of circumstances which prohibit just brute-forcing things; the status quo should change. You can ram through the door and break your shoulder in the process, or fail and jam up the mechanism enough that it probably can't be lockpicked either now, or they broke it or didn't and now the guards heard them do it. You try to provoke the dude, but now he's sure you're just a bunch of hooligans and isn't going to stick around to listen to you more.
Sometimes that's not going to work on its own. Sometimes the player will say "ok, I ram into it again", or "I try to guess at the guy's motives again."
2. The same thing will fail again if done under the same circumstances.
Ok, they've shouldered those doors, they tried to guess at the guy's motives, and failed. You're right, they could justify just rolling that over and over, but you're also right it's not going to be fun. You're also sure this is a case where failure's fun to explore (if it isn't, they should've already succeeded automatically).
This is the time when the group decides "okay, this isn't going to be fun to just repeat. You tried that, you failed. Your dude can do it for an hour as far as the narrative's concerned, but you should try something different." You'll probably need to suggest it yourself. If they think that sucks and aren't sure what to do, maybe you could prompt them, or maybe failure wasn't going to be fun to explore and y'all should talk about just auto-succeeding on this one.
This is the point where they need to explore other options in the narrative. They need to head out, do research on the guy, and come back. They need to find some leverage for that door, or maybe they'll find an alternate route while they're doing that. Force the story to change as a result of their initial failure.
They can try the same thing again, but they can't try it in the same circumstances: they need new advantages, ones that actually make a significant difference. If someone just says "okay, I psyche myself up for this one", and you think it's weaksauce, call it out as weaksauce: Fate's here for dramatic games, not the easy way out.