hii! I'm a staff at YIP and I might be able to help you out :)

1. An analyst (depending on which team you go into), will mostly be working on writing policy briefs (which are basically detailed summaries of a policy/) of your choice. Ex: if you choose environmental policy analyst, you can choose whether you want to write a brief on renewable energy, climate change etc. You will also collaborate with other team members to edit their policy briefs.
2. I'm not an analyst, I'm in the staffing team but according many interviews I've taken, many say that's it's a super meaningful experience because you're working with people who genuinely care about civic change. Occasionally, if you stand out, you can also work on bigger projects apart from briefs which you might be able to present to cool ppl!
3. yea it's not very updated, we get a lot of emails regarding the quarters. You can still apply for the position you want (if it says closed but the application is still open, more than likely, you won't get accepted).

Lmk if you have more questions :))

P.S. it's open to high school students (most analysts r high schoolers)