After restore a backup of mikrotik v6.2 on new one Mikrotik v6.20, router get unstable. It seems that backup file format is different in v6.20

what does 'unstable' mean?..

anyway, you may install 6.2, restore backup and then upgrade to 6.20

Never restore backup on different device or on different version.

I have no problems with restoring backups of 5.xx on 5.yy routerboard RB450G. (I have thousands of these RB450G and no time to configure from default configuration). And no problems with restoring 6.zz to 6.vv (if zz and vv <20).

But with 6.20, the syntax of a few commands has changed, and maybe the format of backup files. So, I have to do as Chupaka said!

Thanks.