Question about starter guilds

So I played a while ago and stopped because I was lost. I've begun playing again and really feel like i'm starting to get it. I made my own guild (pretty much out of ignorance lol) and have started with the starter guild system. I got placed in teir 3 Tuan-taun. I did this wanting to try and help with the raids and I felt like I was, was 1st in the rancor raid that was happening by a large margin.

Then I got my 600 tickets and got bumped up to the next tier of training guilds, Nest of Gundarks. I was banking on the rewards I got from that to help farming character shards from the guild store. There was not opt in, I just found myself in the next tier. I did get what the current guild donated in the mail which was nice and just wondered if the raid rewards might work the same way when the raid ends? Or since I technically left the guild I forfeited my participation?

I am also kind of unclear when a raid ends, do you have to beat all (4?) stages or is there a time limit?

Thanks for any advice and/or answers!