Shin

Yes, you can see [here](https://create.roblox.com/docs/en-us/cloud/open-cloud/api-keys) on how to get a key. As for a guide to authenticate an Oauth app you can see [here](https://create.roblox.com/docs/en-us/cloud/open-cloud/oauth2-sample). If you mean endpoints such as...

Code 400 means you are sending a bad/invalid request, could you send the request you are trying to make?