We known than his real name is Kastsitsyn but he put Kostitsyn on his jersey because it's more simple...
But i heard, that maybe he could bring back "Kastsitsyn" next year! is it true?
Where abouts did you hear that?
As far as I'm aware, he is sticking with Kostitsyn so I'd go with that. I'm probably going to get a new Habs/Kostitsyn jersey before next season and I'll be going with his current name (unless he changes it back of course, but I don't see that happening).
It is probably a matter of personal opinion, but I prefer to put something on the back that will be lasting and that no GM can trade away.
So, instead of a player's name with his number, I chose the following on the white Habs jersey:
On the left shoulder in an upward diagonal direction I have: La Sainte Flanelle in blue.
On the right shoulder in an downward diagonal direction I have: Les Glorieux
Across the bottom of the jersey above the red stripe: Les Joueurs Du Tricolore