One rule: newest first
Your feed is every post from the friends you've added, in the order they posted them, newest at the top. Nothing reorders it, nothing gets boosted, and nothing from strangers ever shows up. There's no algorithm deciding what you see, because the server can't read your posts to rank them in the first place.
The last 90 days
The feed shows posts from roughly the last three months. It's built to be a "what have my friends been up to lately" view that you can actually reach the end of, not an endless scroll designed to keep you swiping.
"You're all caught up"
When you reach the bottom, that's everything recent. There's no hidden pile of posts you missed and no "see more suggestions." You've seen it all, so you can close the app and get on with your day.
Older posts live on profiles
Anything older than the feed window doesn't disappear. A friend's full history is always on their profile, at any age. Tap a friend to scroll back through everything they've posted.
The feed is meant to be finished. Open boopr, see what your friends posted lately, and close it. Thirty seconds and you're out. That's the whole idea.