A: Almost immediately, and yes, it is PERMANENT.
B: Once again, almost immediately and it is PERMANENT.
c) Thrice, almost immediately and it is PERMANENT.
I have been on T since 9/19/2012. Believe me, the difference is like comparing night and day and it happens very quickly (or so that is my own experience, from both endogenous and exogenous sources of androgen).
Further, in the beginning of penile growth (and yes, I consider it penile rather than cliteral), trying to please it is very difficult. There is both too much and not enough there to get the job done and I don't feel you would be very satisfied with it. Trust me. It takes, or so I hear, a minimum of five years for you to achieve full growth and potential with your erectile tissues downstairs. A short, temporary basis on androgens will NOT give you the results you are undoubtedly looking for in only a couple of months or less. You will be frustrated, I feel.
It (also in my personal experience) is PAINFUL in the beginning of the changes (and I suffer from nerve damages, and also have a high pain threshold). From the larynx, to the penis to even the muscle and ligaments. Why? Because it happens a lot more quickly for us than for cismale adolescents. By the way, ligament and connective tissue development, unlike muscular development, is PERMANENT also, and happens just as rapidly as the rest of the changes.
To sum up, this is a very big and permanent decision to make and so I hope you will give it the time and care it deserves. If you have even a shadow of a doubt that you can live with these changes to your body for the rest of your life, then DON'T do it.