So, build multiplayer mode first.
Then when you make solo mode, you'll just change a few events.
If you do it the other way around, you may have to re-event your setup completely, doubling your dev time.
Basic set up would be:
Use the space laser game multiplayer demo (in C3 demo projects) as it auto picks if you are peer or host, save you time.
The host can still play along, their device just actually runs the game.
Host sends all peers a message with tag "question" and message "question text"
Peers send messages to host with tag "answer" message "answer text"
Once all answer, the host updates all peers with the result of that round.
for solo mode, you end up just using your "on Host" and "on Peer" events with minor changes.