I saw vi_VN in Demo site but couldn't use it, maybe you didn't allow changing admin profile
how can I check it?
Two accounts used for demo used are read-only, you can't change profile of them.
But you can create new admin accounts, login with the new one and test vi_VN translation. 
In demo site, there isn't the ftp options when create account.
Yes, we havn't integrated it yet, and we didn't say we already integreated it anywhere.
Ah, I couldn't use the link "Buy now" to buy the iRedAdmin Full-featured Edition. I want some info, specially the price
Not ready yet, but it will be available soon. Just be patient