I actually tried everything. I read MS help pages - there are CIRCULAR support references, that finally leads to the same site - to the same site that not worked.
I also managed finally to speak with some incian support guys, they was really helpful, however they said - after some rounds of mailings that there is NO WAY to recover the accound if that idiot MS account recover site does not recovers it.
So finally - after spending really lot of work on it - I created a new accound and payed that f* Minecraft again to my child. F* MS. F* them all.
Sorry for telling this, but this was really really fristrating...