[How to place a command on an item players can have in their inventory]

Hello!

I was just wondering how to put a command on a object such as a block of dirt that a player could have in their inventory and click it to teleport them to a certain place, such as back to the beginning of the parkour.

 

Thank you!

[How do I create an area that gives players saturation/doesn't let them take damage?]

Hello! I recently made a server with a few of my friends, and following growth I've been making improvements to the server. Players spawn in the sky, and have an optional parkour they can do, but a problem players have been having is taking damage from falling to the barrier blocks underneath them while trying to complete the parkour. 

Is it possible to make an area where players won't be hungry and won't take damage? If so, how?

 

Thank you so much for any help!