Ways to limit access to subsections of websites that I didn't create?

I'm not sure if this is the right place but it seemed the most reasonable place to start.

I want to give a third party access to a website where I am a user (not the creator). However, that 3rd party should only have access to one section. Imagine that I'm giving them my reddit login. I would want them to shitpost onto https://www.reddit.com/r/pics/, but wouldn't want them to access my preferences & change the password https://www.reddit.com/prefs. Hypothetically.

My ideas are

(a) I can somehow route traffic through a proxy & the proxy can fail to deliver the subsections that I don't want. It's a little difficult to set up & it also requires that I set up a desktop where they remotely connect to but don't have permissions to change proxy settings or see the stored password. Plausible, but not optimal.

(b) I did find a Chrome extension that does this however, I can't figure out how to stop the user from just removing the blocks.

Is there another option? Is there a common solution for this? Thanks!