Is it allowed and if not, why?

The category for AMFP that everyone runs is called "Single Segment". That means no exiting to the menu or using quick saving and loading which is basically the same thing as exiting to the menu, but faster. Another reason to ban it is quick saving and loading can only be enabled in the CFG file. If we allow using options in the CFG file then the Debug Toolbar would be fair game, which would just let you load temple from the start.

No it's not allowed as it breaks the fall damage system completely.