I beg to differ from other people answering this question.
Even though the subjects are the same, the stuff tested in USMLE is vastly different from Indian entrance exams.
The best use of your time is to study for step 1 (assuming you’re serious about pursuing USMLE) during your first and second years alongside your regular curriculum. I’ve written posts previously about a strategy for current medical students. If you score well in Step 1, which you should take sometime during your third year, or during your internship, depending on where you are in your training, pursue other steps without trying to study for Indian entrances. You’ll need to give it everything. So don’t thin out your mental resources.
If you don’t score well, your chances of matching are pretty low. Not impossible just low probability. Higher risk. So I would advice to then study for Indian entrances.
I understand the temptation to study for the Indian entrances as a back up. It sounds logical and safe. But it’ll only stress you out and you won’t be able to give your best to either. That would be the worst outcome. So pick one.