How i did the upgrade
Before doing the things i describe underneath make sure to backup the whole forum and database.
Ths way you can always go back to how it was.
on IPB 3.4.x
Put forum in maintenance mode
Remove all themes that are not the default
Remove all plugins that are not invision
Remove all apps that are not from invision
Check if all upload paths are correct in your forum config
Then I rebuild al my caches and removed orphaned and rebuild all attachments also I did topic and comment recounts
You could finish up your tasks with putting your board into dev mode
If your board is in dev mode you get red messages just complete those
after finishing up that put board in normal mode
Check everything once again before performing the next steps
What to do in FTP or filemanager on cpanle/plesk or any other hosting panel
Remove all directories where your forum is installed in but keep
these are directories that contains your pip member ranks, badges for underneath admins or mods and it contains uploads for profile pictures or forum attachments.
Remove all files in root of your installation but conf_global.php the installer needs this file to know your database configuration
If you are using a favicon keep that also in the directory
Also if you are using verification files for webmaster tools in your directory keep them also
If you are using seo friendly urls keep the htaccess file also in the directory
If you have done this all you can proceed uploading invision 220.127.116.11 files and unpack them.
Now lets install 18.104.22.168
it will ask you how people need to login into your new forum
it will ask you wat to do with friends on 3.4.x
the installer will ask you to convert friends to folllowers because friends are now named followers in the new version