Unity Matchmaking questions

Hello, I am quite new to multiplayer development, and I am getting kinda confused with a few things and was hoping someone could help me out a bit.

I followed a few tutorials and managed to get 2 instances of my multiplayer test game to run on the same PC
(Through LAN Host and LAN client) using unity standard networking (I believe it's called uNet).

However now I want to test on several PCs, with my friends that aren't on the same network. I looked around and I saw a tutorial on Unity Matchmaking, which consisted of setting up a few things online and syncing it with the editor, and it would just work fine.

I am using unity personal edition, and it says here I can have 20 concurrent users.

1) When I publish my game, can I have more than 20?

2) If I am still in the development stage, and only testing my game with my friends by sending them the executables to my game, do I have to pay anything ?

3) Does matchmaking link each player to the other or all the players to a server?

4) If two players have different versions of executable can they still play together?

As you can tell I'm not very good at this yet, so sorry for the lame questions, hope someone can help me out.

 

I am trying to understand the documentation but I just can't, it's too confusing to me. Do I need to pay anything to test matchmaking system while in development? (Giving built executables to friends and testing unity matchmaker?)
Does anyone know?

 

Here are some information related to UNET matchmaking and relay servers:
https://forum.unity3d.com/threads/unet-seems-fine.427415/#post-2763031

 

Thanks a lot! So using matchmaking is free during development mode, which is why there is a CCU limit, then once you publish your game to the public, the CCU limit is gone and you need to pay depending on bandwidth usage. Makes sense now!
Thanks!