If you are completely free in these 2 months, then grinding around 3 to 4 hours daily would be considered significantly good, but if you are unable to provide that much amount, then you could stick to around 1 to 2 questions a day.

It really depends on your definition of "top coder," but i think most red coders don't just mindlessly grind 6-7 hours a day. The consensus in the community is that quality and intensity of practice matter far more than total hours spent.

idk about others but me and my bros train like this: topic->contest->editorial->upsolving and it takes around 8 hours with breaks in sum,I found it very useful though

It depends on you,during my summer break i was doing 5 problems daily,something like 2-800,1-1000,2-1300,1400,1500),(5hrs daily),and kept learning from every question which i couldn't solve ,mostly doing questions of desired rating from problemset(recent ones).(I ain't top just sharing my experience)Also,try to maintain a streak which motivates you to continue further(when classes start),so that daily one problem becomes your habit which helps in your long run.