mesh app mobile and light switch client/server

hello guys!

i using the 2 examples of light switch client and server and the mesh app for android all work fine, but i have some questions about those examples:

1. if i provision the ble device using the app and remove the app from my phone and install it again why i cant connect again to the 2 ble device that i provisioned before? and if i cant to connected them want i need to do  that i will?

2. the server can send data over the ble to the client? client to client? server to server?if yes so how?

3. if server can send data to a client (or client to client) and i have number of clients in a group how i send to specific client a data?

thanks!!!