Minecraft limits what the client can do. A client can't magically give you OP on a server, put you in creative mode, give you items, etc. Things like creative mode (along with the others previously mentioned + more) are handled server side, where things like movement, rendering, etc. are handled client side. Clients that claim to do something that's handled server side are a scam, and they could have malicious intent (ratting you, installing a trojan, etc.) and should not be trusted. If you have any questions about what is handled client/server side, or if a module is possible, you can always create a post on our subreddit.