there's an adventure map called atmosFear which needs a resource pack. here's what happens when i try it out on emc
The map depends on items that Vanilla Minecraft doesn't have, which is why recourse packs are used. The creator can add many new blocks and items by retexturing existing ones. So, iron blocks may be computers (a block not in MC) so you'll have a beacon drawing power off of computers.
Hell is allowed. Hell, I wouldn't even call it mild language, just normal language. I can't actually think of any context where I'd consider it even iffy...
I'll accept the fact that "hell" is allowed, but I won't accept someone saying something like "Go to hell"
Basing this on PG age rating alone, in the UK at least, I'm 99% sure "go to hell" is considered PG (going on the basis that BBC R1 is PG, which I'm fairly sure it is) - although the US does seem to be waaay more oversensitive about that sorta stuff. However, if directed at another person on EMC, it's a rule break.