Ok, it won't work if you're doing it on 0.3.7 version: https://wiki.rage.mp/index.php?title=Player::setClothes
There you have a workaround for it to work.
I guess you'll need another link before starting using resources, you're missing the basic knowledge:
https://wiki.rage.mp/index.php?title=Getting_Started_with_Development
El server funciona con la versión 1.1 (aún en beta), no con la que viene por defecto en RAGE (0.3.7)
En el siguiente hilo viene la rama que tienes que poner en el config.xml para cambiar de versión:
Did you try to do what the warning window says about verifying the cache (if running Steam version) or executing PlayGTAV.exe (if using Rockstar Social Club version)?
That question has no sense. The syntax is more or less the same (talking about the API), so it's up to the developer.
You should know which language is the one you know better.