What constitutes a legal separation (as per Indian laws) between a husband and a wife living under separate roofs?

A couple could be living be under the same roof but not living together as husband and wife.

So non-performance of martial obligations towards each other. Not have conjugal and sexual relationship with each other would constitute as "legal separation".

There is some called as "judicial separation" as well, which is basically the Court passing an order to he effect that the couple shall not be under an obligation to cohabit with each other.

Can you train legs and back on the same day?

You can, if you are smart about your exercise selection, and your intensity levels.As a natural trainee, you should consider training each muscle group more than once a week, so at least twice if not three times a week, to give yourself enough

How, if at all, is the accent, pitch and voice of gay men different than that of straight men and how accurate is voice in determining sexual orientation?

There is no reliable way to tell if someone is gay by their voice. Given that 1–3% of men are gay, have you had the impression that 1–3 men out of 100 you come across every day have

Why don't I feel tired until 4 am?

You've probably got insomnia. Listening to music while trying to fall asleep can really help. If that doesn't work try meditating or just laying in bed and closing your eyes. There are probably videos that are design to help you fall asleep too. I have insomnia myself and it can be a pain