I have an old phone which I used for a few month when my S4 was broken. I managed to backup and restore the app data from S4 to this phone by just copying
/data/data/appname - however both devices were 4.x .
Now I have a new phone with 6.0 Marshmallow and I intended to do the same thing - and failed.
Example whatsapp: I copied the old apk, installed it to 6.0 and then (in twrp) replaced
/data/data/com.whatsapp with the old one.
For testing I also set it to
chmod 777. Whatsapp shows a notification (A problem with chat history) and if I start whatsapp it closes (crashes?) immediately.
Any idea how to copy the old app data to marshmallow? thanks.