I'm trying to modify my cheap Chinese Bluetooth speaker with JieLie chip (AC6965E i presume) but i found no info about how to program this damn thing, only your guide on the older version.

I'm trying to modify its starting sound, connect, disconnect and low battery sound into something less ear splitting. And hopefully reprogram it to do something more useful (like notify connected devices).

A few extra questions:
How to dump the whole flash to make a backup?
Does the AC6966B SDK work with this?
Does the BR25 firmware structure the same as BR17?