1. Multiplayer work on many layout or it's better to do all (the game) on the same layout? My game is like a naval battle game or chess game.
Layout count does not make any difference. Single Photon object is always available in event sheets.
2. In Scirra multiplayer plugin, only local variable that I want to share with other player are share with the module "send message". Can I do the same thing with your plugin ? I have no character in my game only a board.
Photon plugin mostly provides a way to send messages with event number and string event payload to other players joined to the same room. To share local variable, you need to send its value as it changes and update values on other clients from message payload. In some cases you may find 'room properties' or 'actor properties' more convenient to share a value.
3. In the scirra plugin if the host disconnects the game is over. Here I would like to make sure that if one of the two players disconnects he can continue to play until one decides to leave the game or no longer plays for a while. Is it easy to set up? How can I save local variables from each player and keep safe on both player side all the values?.
Join action has 'rejoin' parameter which allows to rejoin with the same ActorNr as client had before unintended disconnect or 'Suspend' operation. Call 'Set suspended player live time' before room creation: client will be able to rejoin only during specified time in seconds after disconnection. 'Set empty room live time' action sets the time during which room exists after last player left the room allowing rejoins .
4. What is the best plan if I have 500 players online and what is the cost ?
500 ccu for $95/month
5. ...(I suppose C2 plugin is also compatible with C3?)
There is C3 version of plugin in SDK package.
6. Do you have c3 examples or only c2 examples ?
Provided examples work with c2 and c3.