You don’t require immediate support. You just need to read the bloody error message and follow the instructions.
Edit: I’m pretty sure it’s said somewhere that adding mods to FiveM will make it even more unstable so, why did you think it would be OK to add them in the first place?
Yes, it does. Like it says in the link you’ve posted, its a modification framework (the framework for the addons the community makes with C# and Lua). This doesn’t mean it will support third-party mods.
Also, if you’ve read about, you should also know that FiveM hooks into GTA V’s code which (I think) is why it’s unstable to begin with (because GTA’s code isn’t open source). So, adding a third-party mod on top of this mod makes it even more unstable (it’s basically a hack put into another hack). This is why the devs say to get the best experience, you should remove all other mods.
The error message asks you remove it… Remove it and it’ll probably work. If not, then it’ll be another error causing the issue.