1. It's all practice. For the fig. 8 and U turn : An hour or two in a car park and you'll probably have it down. Bit of back brake, steady throttle, enough lean, shifting your weight on the seat, fine clutch control, not too slow so that you fall, not so fast that you go wide, head turned and eyes focused on where you want to be. Once you have the confidence, you'll be fine.
2. You can fail, but probably not for the stall, more for how you recover from it (or don't).
3. Yes, do a full car park lesson if you can. Bit boring for the instructor but worth it.
4. Depends. If you already drive you'll understand much more about general roadcraft. Observations are very important, also cancelling indicators. Easy things to forget.
Your instructor will be able to give you a good idea of how many lessons you need. They won't want to put you forward before you're ready.