As far as I know unacademy provides 20000 free live classes and the categories which are available are UPSC, BANK EXAMS, RAILWAY'S. It is developed to promote the spirit of learner's during this pandemic.

If you want to study for NEET 2021 start from the basics and then study the harder subject so that when you study the full topic your confidence builds up automatically and then you can go through the previous question papers to have slight idea of how the question paper is. Hope you are satisfied with my answer