1) How is most popular calculated for game jam games. Is it based off the number the said person has voted for, the number of poeple that 've seen the page or ...?

2) and when you"major update" a project that was in new and popular before will it be in new and popular again. I think it should :P XD . And if you make it cost money when it was once free then will it still be in new and popular?

3) oH, and if something is put on sale (e.g. the summer sale) will it have a higher chance of getting spotted and downloaded (I know nothing of sales)

1. The popularity algorithm is secret and deliberately obfuscated so people don't try to take advantage.
2. Yes, if you post a devlog marked "Major update or launch", our staff will look over it, and if they approve, your game will be placed at the top of new releases again.
3. In my experience, sales are hit-and-miss. It's worth a try, but don't hold your breath.