Yes, there's no problem with playing with demo version.
If you have to play someone who also has it, you'll have to play rematchs until you finish the match. If you get to a tie break, host a 0 games per set match.
Tour issues by PM or Skype.
If you don't add me nor send me a PM, you might see your chances reduced. Inform me about anything that might have went on with your matches BEFORE deadlines, otherwise, decisions won't be changed.