There is way to delete 2nd Homey - How to remove my old Homey? - #2 by Peter_Kawa - it’s somehow similar even in the new app - it’s there, please search a little bit 
Very strange. Have you waited after restore after all apps downloaded ? Like 5-10 minutes ?
Sorry for that, there are many cases where the backup did work fine. Just what I can think of, you were on old Homey on the latest firmware, correct ?
Yes, when you uninstall app, devices get deleted - upon re-installation, all devices would stay.
