Yes, you can downgrade back. Basically you follow the same process (with one additional step):
- delete the new OS from your PC (that's the added step)
- install the old OS and delete VENDOR.XML
- restart Desktop manager and it should loadthe old OS (after warning you that you are going to downgrade).
The only issue I have had with downgrading is my Address Book didn't get restored (and I've downgraded my 2 devices several times).
I recommend making sure you have a clean backup of your 4.2 device (not the backup made during the upgrade - a separate stand-alone backup). Open up the backup file using Desktop Manager -> Backup/Restore -> Advanced and then make sure the Address Book shows records.
My 2 cents.... I had to restore my Address Book from an old backup 4.3 backup (I have a Curve) as it would not restore from the manual 4.5 backups I took.
__________________ No longer a BES Admin, but it was fun while it lasted!