As long as you have you have the correct GCSE grades and 2 A levels then you can join.
Yes ... plus confidence, initiative, sufficient outside interests, motivation, leadership skills, a good level of fitness, a spotless medical history, a knowledge of current affairs and the RAF, and the rest!
The oldest age you can be is 23 and being 23 on the day of OASC if I am correct.
No. It depends on branch, and it is counted from the date you start training. For some branches you can apply well into your thirties, or even older for medical, dentistry, etc.
Look in this thread, you will find all your answers what you post in this thread.
Also try the RAF careers website, which has info on joining ages, the application process for graduates, etc etc.