you will create a mini-tournament.

Ravinn wrote: As I can challenge multiple opponents to a friendly game, so I wonder what will happen if I didn't withdrawal as well.

You can only play one friendly each week. If someone accepts one of your challenges, or if you accept a challenge from someone else, all other challenges made by you or to you will be cancelled automatically.

Because of this, it's not a bad idea to challenge multiple teams to friendly matches to increase your chances of getting a game scheduled. Teams you challenge may get multiple challenges but can only accept one.