Yes, you can simply download/install appropriate version, it will not hurt your data. Are you sure it's related to upgrade?
Once you'll downgrade please let me know if it's getting fixed? I'm asking because we also have lots of data, pictures, and all is good after upgrade to version 3.15, therefore I'm wondering...
If you want us to take a deeper look in to this issue please send me data sample to

, no need to send whole data file, you can create new empty data file using File -> New menu item, and place few sample notes inside.
AllMyNotes Organizer usage idea: password-protected
contact manager app, use alarms to be reminded about anniversaries, birthdays, important meetings, and even calls!