During the summer how much should I revise?Watch
Better state year 12 is in the less you have to do in 13.
Do you have any coursework or epq you can research?
Get a job and earn money to be used for uni deposit, revision books, open days and presents.
Just enjoy the break and get your MH in good order.
Depends on your target grades. If you're hoping for an A* for your finals but have only been obtaining B/low A, definitely revise the topics you're struggling with as you won't get much of a chance to in year 13 (the course (for most subjects) gets harder).
No need to do too much, just a few hours a day is fine (as long as it's consistent).
I would start to think about your personal statement, especially if you're applying to Oxbridge (as the deadline is earlier). After writing it, give it to parents + tutor to read and constantly evolve it.