To who does this belong?
- To whom does it belong?
- Who does it belong to? (preferrable)
To whom it belongs
whom does this belong
‘To whom does this belong?’ is the grammatically correct term, but as the English language is evolving, more and more native speakers are using and accepting ‘who’ in the way you have used it.
Who does this belong to?" is less formal and may, as Tort suggests, be preferred by many people, but others dislike ending the sentence with ‘to’.
‘To whom does this belong?’ is correct but very formal and should only be used in written English.
‘Who does this belong to?’ is the normal spoken expression.
Is there an echo in here? 
Is there an echo in here?
an echo in here?
'n echo out there
Aha! A facsimile of an echo!
Aha! A facsimile of an anchor!
No… I must be the real thing. I often hear people calling me an anchor… something like that anyway. ;D
this is as clear as mud )
I thought you were keeping up extremely well, but we should probably stop now as it will certainly confuse less aware learners.
you’re a leaner too??!! ))
Leaner? Are you saying I’ve lost weight? Thank you!
We are all learners of something, Sergey. I hope that the day I stop learning will be the day I stop breathing.
you confused me completely ) you’re learning how to breath or what? ))
I will tell you - you bring it in and than out, in and out ))) simple. don’t take too much though )))) otherwise you’ll be flying )))
I can’t love this no more, BN! 
BN means life is a process of learning, Sergey. Just for clarification, Beeesneees is a native English teacher, who still keeps learning, though.
She is a native English teacher??? ))) That’s where all her brilliance comes from )) That explains almost everything! )
I’m still wondering though whether she’s a soft or a strict teacher ))