very challenging project to create bluetooth mesh for creating local decentralised network without internet connection on the case A,B . The case C is the easy part as his friend already connected with satellite internet , to broadcast all the note .

case A and B is rather challenging . man can use library mesh networking like bluetooth mesh SDK or googles nearby connection API. but the bluetooth as it named have very limited range like man should be approx 100m , depending on the bluetooth type . also latency and bandwidth , man cannot post many images or video on that A and B situation .

It is doable to create offline network messages using BLE (Bluetooth lower energy ) Mesh .