1.) What is the exact way to contact people via phone if those people do not have phone?

2.) And yes, organization among 12 years old means that someone writes "lets do X" and other write back "cool". Those available show up. Those not available sometimes talk back and negotiate different time.

3.) If 5 12-16 years old kids organize in a group chat, not being on that chat means missing out spontaneously organized actions. Even if they are unusually serious and recall to call your parents instead of just jumping into action, you are not there to have input into agreements. So, the meetup will be when you are not available and it will be too late for you.

4.) And yes, even among adults, if others have to jump through special hoops to join you specifically whereas everyone else does not have such requirement ... you will miss out.

Yes, 12-14 years old act on impulse and organized spontaneously without creating org chart around it. That means forgetting to do extra steps so that people not being in chat even know what you are about to do.