how to import user info such as nick name and passwords

Reinstall your old version of dolphin then use your back up database by going to admin panel >tools>database backup>database restore and import your backup database file.Next run the database upgrade for 6.1.2 and then backup the database after database upgrade .Now install 6.1.2 and after that go to admin panel >tools>database backup>database restore and restore back ur upgraded database.

Reinstall your old version of dolphin then use your back up database by going to admin panel >tools>database backup>database restore and import your backup database file.Next run the database upgrade for 6.1.2 and then backup the database after database upgrade .Now install 6.1.2 and after that go to admin panel >tools>database backup>database restore and restore back your upgraded database.