1)is it normal to be given oppotunity to choose stage 2 and 3 tests + interviews date, 1 day after i submitted application.
I received a reply within a few days, they will email you letting you know whether you can progress to stage 2/3. you will then be able to view your online application to book a slot.
2)are tests/ interviews granted for everyone who submitted their application.
No
3)what maths/ physics do i have brush up before stage 2/3 ?
Put aside a week to digest this thread in its entirety! It contains a massive amount of info, there's nothing worth adding that's not already been discussed.
Forgot to mention... Good luck!