Downgrade Yosemite from back-up (not Time Machine) I've read some questions and posts regarding Yosemite downgrade from Time Machine back-up (like this and this) but I was wondering if the same thing would work for a bootable backup made with Disk Utility. Will this process work?


Boot the Mac from Recovery HD
Enter Disk Utility
From the restore tab, choose the internal hard drive as destination and the bootable drive as source.
Restore


Are there going to be problems due to Yosemite change in drive structure? (as suggested by this answer, if I understand it correctly)
I would not use Time Machine in this case, use SuperDuper! of Carbon Copy Cloner to make a bootable image on another drive, upgrade, see how it is and if it fails to work, then go boot off the bootable image and clone it back to where it was.

I would suggest taking a Time Machine backup in addition so you always have 2 copies of the data.