I am currently working on an UWP quiz app for Windows 10. It's intended that the player can purchase items, VC... As you mentioned many times, you don't "trust" the client, it's not recommended to allow the user to increase/reduce VC. The recommended way would be to implement this via cloudscript.
Now that I am on the essential tier, there is a limit of 15 cloudscript executions. Does that mean if 20 players execute via cloudscript that does not work for me? Could you explain what does this limit mean? 15 times per hour, for all players of the game?