One question: if my coins already in C-Cex (I've send earlier for swapping to v.5), sould I re-receive from C-Cex and re-send them to C-Cex one more time?
as long as they are on C-Cex no need to additional resending. Change of wallets is done by the exchange. Then once you want to withdraw you need to get the newest version of the wallet.