Firstly: "o'clock" should not be used except after a number of hours, alone. "12 o'clock", yes; "12:01 o'clock", no; "noon o'clock", no. If you need to be clear that (for example) "ten fourteen" is a time, and not some other number, you could use "a.m."/"p.m." or say "fourteen [minutes] past ten".
Secondly: "on the dot", "sharp", and others are used to emphasise that a time is precise when people might think it's not. If I say "12 o'clock", you might well assume that I'm rounding to the nearest hour (or half-hour, or 15 minutes, or whatever). I could say "12 o'clock sharp" to be clear that I mean exactly 12 o'clock.
If I say "10:23", however, the fact that I bothered to specify a number of minutes, and not a nice round multiple of typical values, would suggest that I mean exactly 10:23. Saying "sharp"/"on the dot" would be redundant in this case, but not wrong.
That said, there are situations when even an atypical number of minutes might be taken as vague, and so "sharp"/"on the dot" would not be redundant:
When accuracy to within seconds is meant, and you want to be clear that you mean "10:23 and zero seconds". (Example: A school has morning break start at 10:23. The students want to be let out 30 seconds or a minute early, but the teacher is adamant that they will be let out at "10:23 on the dot".)
When atypical numbers of minutes are still only estimates. (Example: Bus timetables will give times like "10:23", but it's expected that it will likely be later. You might then tell a friend that the bus arrived at "10:23 on the dot", because you want to emphasise how unusual it was that it was there right on time!)
Lastly: "high" is (in my experience) only used with "noon"; not just the time "noon", but with the exact word "noon". The title of the movie you linked to, "Twelve O'Clock High", is not about time, it's about direction. In a military (or colloquial) context, directions relative to you can be specified by points on the clock: "12 o'clock" is straight ahead, "6 o'clock" is behind you, "5 o'clock" is behind you but a little bit to the right. And then aviators, having to deal with three dimensions, can also specify "high" or "low" (or, if I remember rightly, "level"). So the title "Twelve O'Clock High" is pilot-speak for "straight ahead and at a higher altitude".
Actually I would argue that 'whatever' is synonymous with "I don't care". However, there are certain circumstances when "I don't care" is used.
Here are some that I can think of:
Getting into an argument about something, and brushing the accident off with 'whatever'. Note: This may not be the best way to use 'whatever' to look cool, because it is somewhat rude and dismissive as @ColleenV mentioned (dismissive: feeling or showing that something is unworthy of consideration).
Person 1: Since you were late to pick me up, I missed my appointment!
Person 2: Sorry, but there was a lot of traffic.
Person 1: Whatever
(meaning I don't care to argue about this anymore)
Losing your train of thought — where you are talking about something but completely forget what point you are trying to make.
Person 1: I know there is something that I need to buy at the grocery store, but I can't remember, and I forgot to write it on my grocery list. Ah, whatever!
Best Answer
"Beat the game" is probably the most popular way to say that you completed a game. However, it does not necessarily imply that you have completed "everything possible", like OP is asking. It's more likely to imply that you completed enough to see the "ending", which is especially misleading if the game has multiple endings, and even more misleading when there is only one true ending, per se.
It means that every level was completed if the game has to be played in a linear/sequential manner (eg if every level must be completed in order to progress complete the game).
To be explicit (which is what OP seems to want) that you completed every level or mission, you should include something, like
Actually, the example in your title seems a little formal, but fine nonetheless.
If you and the listener understand that you are talking about a game, then "in the game" seems redundant.
These all seem fine, but 2. sounds the most casual.
These questions sound fine, but they do not necessarily ask whether or not the listener has completed every level/mission. As you know, in some games, you can play the whole game, but not complete every single mission/level. (I cannot think of any at the moment.)
Some alternatives are "pass", "beat", "complete":
I think "I passed the whole game" and "Have you passed the whole game?" might sound strange. This list is not meant to be exhaustive and I'm sure there's plenty of slang out there that will work.