Once I put my sd card In I no longer get notifications, I want to get notifications and I don’t know how without removing sd card

Please re-install the app.

Can multiple camera be installed at the same house? If so, is signal interference a problem and can you view all the cameras from the same account on the app?

Mutiple cameras can be isntall  in same wifi. 

You will have access to all camera feed in the app.