I hope all the below form of sentences give ‘Passive’ meanings, am I correct?
1) be + verb3 [i.e. past participle]
be prepared.
2) being + verb3
being processed (but in continuous form).
3) getting/get/got + verb3
getting married.
Yes, absolutely correct! (Apparently that answer is too short: "Body must be at least 30 characters; you entered 24.") . So I'll try again:
Yes, absolutely correct! Those are all passive.
Yes, but all of them have different semantics.
Being + V3 is not grammatical by itself, but you can add copula (to indicate continuous aspect version of be + V3) or use it as gerund. Basically, being + V3 is just a conjugation of be + V3.
For be + V3 vs got + V3, look at this answered question: When do you use Get or Be in the passive voice?