Came back to my 2022 account after years away. I build things and want to participate without being "that guy". What should I know?

Hi all. I made this account back in 2022, barely used it, and recently came back properly. I've been commenting for a bit and I'm slowly getting how things work, but I'd rather ask early than learn by getting banned.

Some honest context: I'm a software developer. I build things, some for international users and one free tool for people in my own country. Naturally I'd love for people to eventually find them. But I've read enough threads to know Reddit has strong feelings about self-promotion, and I've seen how badly it goes for people who show up only to drop links.

So my questions for people who've been here longer:

1. What's the actual etiquette for a builder sharing their own work? I keep seeing "9 to 1 ratio" mentioned in some places and "just read each sub's rules" in others.
2. How long or how much should someone participate in a community before sharing anything of their own?
3. Is it better to mention you built something only when it's directly relevant to a question someone asked, or are dedicated "I made this" posts okay in subs that allow them?
4. Any mistakes you see returning accounts like mine make that I should avoid?

Not linking or naming anything here on purpose, this post is about learning the norms, not promoting. Appreciate any wisdom, including "you're overthinking it" if that's the honest answer.