VladMal

@Jim M Thank you. I have found out what is that. Previous developer simply copied init.php and made few changes. This why this file has such header and this why it is not updated. My developers fixed this issue! Thank you for support.

Gentlemen, I'm really sorry to ask may be silly questions, but is anyone has an idea what is init_extern.php file is? It was in old version and allows to call memebr data including creating/login, etc. Accordingly to what this file has in the header : * @copyright<->(c) Invision Power Services, Inc. It was a part of the system. What is not part of the system any more (or shall to be changed to somthing else). Thank you in advance.

Thank you @Marc Stridgen, Thank you @Afrodude for your help. It was really helpful. I have upgrated using your instruction and all went fine. Thanks!

Thank you! but I have a couple of questions: (1) where I can get those files? In backend I have only update to latest version button, that's it. (2) I have 350000 + users and 1000000+ posts. This manual update will not brake all that? Our company purchased other coumpany who use this tpe of forum. So I know NOTHING about it, but this forum is quite active and has long history (previous owner not updated it for really long time)....