I see a lot of newborn games use Demo versioning for allowing us to play extremely early product that not even close to actual release. However, Demo, at least in my humble opinion, stays for limited free access of finished product, what we can play to decide if we want to buy full version of the game.
Demo should not be for Testing. This is simply misleading to end users.

Add additional category for projects which main purpose of existing is to test the project in its early stages (including very short stress testing for multiplayer games and this kind of similar things).

Restrict adding projects as Demos which main purpose of existing is far away from tasting released or upcoming to release of original product. Demo versions should reflect >% of game mechanics of original product or should be updated.

Details of what to count for differences with original and other things are objects of additional discussion.