To answer your second question, RVs are specifically designed so that the generator (or inverter) cannot backfeed power out the shoreline plug. If they did that, it would be a substantial safety hazard (energized plug when not connected, for one thing) and a violation of electric codes.
If there's an automatic (or manual) transfer switch, it's specifically designed to not be able to connect the generator power to the shore power cord, but still permit one or the other to be connected to the electric distribution panel. Manual transfer switches are very very uncommon in RVs, for reasons I don't entirely understand.
If there's no transfer switch as such, then usually the connection is accomplished by plugging the shore power cord into a socket connected to the generator output, and feeding the electrical system normally.
