What happens if you play a mod from older versions

This will probably be closed but I wanna know

the game will have error because 2.2 has a diffrenent format than 2.1

It's not going to work properly in 2.2. Depending on the version the mod was made for, textures and sprites will display with the wrong colors, scripts will break or simply fail to work, custom objects will display and/or behave incorrectly and if it's too old, the game may even completely misinterpret the map format it uses.

yeah, what Tatsuru said. I tried it recently and if the mod actually works, a lot of things will be broken. For example, The Sonic 06 level pack has completely wrong colors on all the textures and things like the speed pads don't work. Makes for a crummy experience.