The rules are actually global, not subreddit based. If more than 10% of your posts are OC you can be banned.

>You should submit from a variety of sources (a general rule of thumb is that 10% or less of your posting and conversation should link to your own content), talk to people in the comments (and not just on your own links), and generally be a good member of the community.

That depends on the sub, and what you link to. If you link to something commercial immediately, that’s different than sharing product of a hobby or interest, or something commercial that’s popular and you’re asked to link to a sale site. There are some subs explicitly about things you made, though. If this wasn’t discouraged reddit would be people advertising 24/7. It basically is anyway, but it has to be discreet.

Overall people on reddit love seeing ‘a photo I took’ but it’s true that “here’s a photo my boyfriend took and was too shy to post on reddit” is better.

Perhaps we frequent a different set of subtests, I don't recall seeing anything like this.