If he has parental consent, yes.
No that is illegal.
An 18 year old girl can marry an 18 year old boy even if they are not in love in this state.
Yes he can marry with 19 year old Nepali girl and after this she can also get citizenship of india.
Of-course they can!
In most countries, no.
legally no that is basically robbing the cradle, if you know what that means, and why would you want to marry a 18 year old girl if your a 15 year old boy anyway?
No.
if they both have parents consent
yes. in Bangladesh a 3 month old baby girl and 11 month old baby boy were married.I don't know when, but somewhere between2013. the babies are the youngest to marry.
Yes
With parental consent, yes.
Not if the live in Norway.