I would love it if the first star of the day was required, but the second was a bonus. I love Advent of Code, but I don't have the time to get 50 stars.
No stars are required at all. You can also skip some days if you don't want to do them. Or only to the first stars. However you like. First/silver stars will also increase your score in the leader boards.
I think you need all stars to do the final puzzle.
That might be true, I've only completed it once a few years ago. But if you don't want to the more complicated parts, then you want to skip the last one for sure.
I might be mistaken but I believe the final day has only one puzzle, but the 50th star (a.k.a., the second star of December 25th) is given for having solved everything else. I don't think any puzzles are "locked".
You're right. The second star is a freebie for completing the rest.
Same. Especially when it gets really hard later on. Despite studying CS, I still struggle with it.