If I upgrade MySql base UBBT from 5.5.1 to 6.0 br1.
Can i use UBBT 5.5.1 and UBBT 6.0 br1 with new database format concurrently? []/forum/images/icons/confused.gif[/]

Nope, not possible. []/forum/images/icons/frown.gif[/]

To many changes to the db.

Related post:
https://ubbdev.com/threads/php/...ew=collapsed&sb=5&o=&fpart=1