1 - it depends. The clitoris and the penis are anatomically similar organs. Until a fetus begins to develop sex specific traits, it's all kinda the same starting point. It will never automatically have a urethra routed through it, nor will it ever ejaculate semen or sperm. But, in most, it does get longer and wider to some degree. The longer and wider it grows, the more penis-like in appearance it becomes.
2 - it depends (seeing a theme?). Most guys will experience some growth. Some experience next to none. Some experience a lot. I would say it's highly likely you will see growth but it's not guaranteed and to what extent it grows is purely genetic and you'll really have no idea until it's done.
3 - if you are on T for any period of time and have experienced growth, it most frequently will not revert to its original size. Again, it depends, and you might see some shrinkage but it's uncommon that it would go completely back to how it was.
4 - it functions the same as it does now but on a larger scale. It will get erect when you're aroused (though it is tethered down with ligaments so without surgery, it's not like a cis male erection). Technically, the clitoris does as well, but it is usually so small it's not super noticeable. It will still be sensitive to stimulation, you can still orgasm through that stimulation. How you prefer stimulation may change because size will affect how it can be "handled".
This is one area where your mileage may really vary. Some people get next to no growth. Most get some, some get a lot. You'll have no way to know until you stop growing, but it is one of the first changes to typically start developing. For me, I had changes in the first week though it took until just over 1 year to finish developing. I was lucky in that department (or unlucky depending on how you're looking at it) and had a lot of growth. But it is highly highly individual.
