I agree with Jmat.  Stuffy British people and librarians say you don't end a sentence with an article like "to".  They want to say "To whom is this song dedicated?" just so the 'to' is not hanging off the end. But all normal people in the US would say "Who is this song dedicated to?".

Should I say "To whom this song dedicated is?" or "Whom is this song dedicated to" or how?

"Whom is this song dedicated to?" is technically the correct version. The other one could be said as "To whom is this song dedicated?". The latter form is very formal, but not nearly as formal as using 'whom' instead of 'who'.

In modern English, 'whom' is very rarely used. It's hasn't completely fallen out of use, but it's usually only used in academic contexts. Unless you're writing a technical article or a paper at the level of a Master's degree, you should use 'who' instead of 'whom' every time.

I sometimes write 'whom' <em>only</em> in the forms 'to whom' and 'for whom', but I'd get odd looks if I used it in conversation.

Here are the options, from most natural to most formal:

"Who is this song dedicated to?" > "To who is this sing dedicated?" > "Whom is this song dedicated to?" > "To whom is this song dedicated?"