Want to add some features with Commands or Redstone circuits to my Minecraft server, how?

The functions are quite complicated. Maybe you know Minecraft Varo. It's actually a YouTube project, but I'm doing something similar with some friends. A few questions are still open:

1: If a player joins the server he should be kicked after exactly 30 minutes, because the whole thing is a PvP event and you can't leave the server during the fight. The trouble is that all players come online at different times, so everyone is kicked at a different time.

2: As you might know from Hunger Games or Survival Games, the Border should shrink after each kill.

The first one is definitely a plugin (selfmade). Gabs is not determined yet. Would you have to find someone to program it for you.

The second one I'm not sure if the vanilla goes…

In which Minecraft version does the project play?

In Minecraft Pocket Edition. Because in the latest version (11)

I do not know sorry for Pocket Edition

Okay, but the commands are mostly the same

Terabyte in Pocket Edition does not work that way