1. Currently there is no flasher tool available for general public. Flashing is only possible on care centers (or by Jolla employees). This means that you need to be carefull out there when beeing in developer mode, if you brick your device it can take some time to get device to care for reflashing (and on worst case you may have void your warranty for example if you have overclocked and fried the cpu with custom kernel module while beeing in developer mode). However we are working on possible flashing solution to be available for developers during 2014, but there is no decisions nor ETA defined yet. 4. Most likely by sending source code request to address which is stated in about device settings page.