Engage has a wide range of more or less connected meanings. You can engage an employee (give him employment), engage a gear (make it active), or be engaged to marry (pledged), etc.
The underlying senses of engage involve commit, pledge, become involved with, attach, deriving from the rare/archaic/obsolete...
gage: Something of value deposited to ensure the performance of some action, and liable to forfeiture in case of non-performance; a pawn, pledge, security.
Deploy derives from Latin displicāre (to unfold). Originally this was only normally used of military forces, troops, in the sense of to open out so as to form a more extended front or line.
By lately, particularly with reference to mechanically-activated weapons systems, the two terms have both been increasingly used in the sense of employ, use. It's a bit fanciful to say they actually mean anything different in OP's context, but if Captain Kirk on the Starship Enterprise were to issue the orders...
1: "Engage photon torpedoes!"
or
2: "Deploy photon torpedoes!"
...the first could be interpreted as an instruction to prepare the torpedoes for use, and the second as an instruction to actually fire them. The words are used so loosely that in the above context, they're really synonyms - but if you ask "In what sequence would Captain Kirk give these orders?" (a loaded question, implying there must be a difference), I suspect the vast majority of native speakers would say "1 then 2".
In Modern English, according to the OED, access is defined, in this context, as "The power, opportunity, permission, or right to come near or into contact with someone or something; admittance; admission."
Entry, on the other hand, is defined as "The action of coming or going in," in this context (while the word does have a definition listed which is synonymous with access, that definition is considered obsolete).
In other words, to gain entry into the building means to get into the building. This can be done sneakily, or with permission, or even by brute force, barrelling your way in.
On the other hand, to gain access literally means that you have gained the power or "permission" to enter the building. You are being allowed into the building by the building's security (whether this security is a system of guards or a computer system), or you can reasonably get past the guard.
Obviously, this can be done in a number of ways, from hacking into a computer mainframe to access security keys, to pickpocketing a guard for literal keys, to dressing up and presenting yourself as a high-authority figure, to buying an admission ticket. However, at this point in time, if you have "gained access" to the building, you now have what can be essentially described as an unlocked and unblocked pathway into the building.
If you get in, you have gained entry.
If you are allowed in, you have found a way you can get in easily, or if you have gotten in and you pose little risk of being removed, you have gained access.
Best Answer
Harangue and rant can be used as either a noun or a verb, but tirade can only be used as a noun.
Harangue as a noun is a lengthy and aggressive speech given to an audience of some sort. Harangue as a verb is lengthy and aggressive speech directed at someone or some group in particular.
Rant as a noun is interchangeable with tirade. Rant as a verb is somewhat different than harangue because it isn't directed at anyone. When you rant, you're making a lengthy, angry speech to anyone within earshot. Tirade and rant can be used to describe angry writing, and I associate harangue with angry speech only (AmE).
A tirade can only be a noun, and is more commonly used than harangue. It is very close to both a rant and a harangue, but it doesn't have the sense of being addressed to an audience like a harangue does, nor the sense of not being directed to any particular audience that rant does.