Yes, the battery status can be called up in the app.
If your key is inside and you don't have a priority circuit (you can't insert the key completely into the lock from the outside), you will need a locksmith to access it ;-)
Bridge, FOB and Keypad remain compatible with the 3.0 version and do not have to be purchased additionally (only the old, black magnetic door sensor from the 2.0 version is not compatible and has been replaced by the new (white) door sensor).