1. For example the longest webm - Can't do that since the booru doesn't store upload lengths afaik.

2. the post with the highest score - liborek's post: https://sakuga.yshi.org/post?tags=order%3Ascore

3. the most favorites - Can't see a way to do this

4. the shortest upload - see 1.

5.the most popular genga, - https://sakuga.yshi.org/post?tags=order%3Ascore+genga+

6. most popular copyright/terminology/artist and so on. - See Kvin's post

7. I would also like to know what the most popular scene of each year

2013 - https://sakuga.yshi.org/post?tags=order%3Ascore+date%3A2013-01-01..2013-12-31 (The Booru only started on 2013-08-16)
2014 - https://sakuga.yshi.org/post?tags=order%3Ascore+date%3A2014-01-01..2014-12-31
2015 - https://sakuga.yshi.org/post?tags=order%3Ascore+date%3A2015-01-01..2015-12-31
2016 - https://sakuga.yshi.org/post?tags=order%3Ascore+date%3A2016-01-01..2016-12-31
2017 - https://sakugabooru.com/post?tags=order%3Ascore+date%3A2017-01-01..2017-12-31
2018 - https://www.sakugabooru.com/post?tags=order%3Ascore+date%3A2018-01-01..2018-12-31
2019 - https://www.sakugabooru.com/post?tags=order%3Ascore+date%3A2019-01-01..2019-12-31

8. how many new uploads there are each year.

2013 - https://sakuga.yshi.org/report/post_uploads?start_date=2013-01-01&end_date=2013-12-31&limit=29&level=
2014 - https://sakuga.yshi.org/report/post_uploads?start_date=2014-01-01&end_date=2014-12-31&limit=29&level=
2015 - https://sakuga.yshi.org/report/post_uploads?start_date=2015-01-01&end_date=2015-12-31&limit=29&level=
2016 - https://sakuga.yshi.org/report/post_uploads?start_date=2016-01-01&end_date=2016-12-31&limit=29&level=
2017 - https://sakugabooru.com/report/post_uploads?start_date=2017-01-01&end_date=2017-12-31&limit=29&level=
2018 - https://www.sakugabooru.com/report/post_uploads?start_date=2018-01-01&end_date=2018-12-31&limit=29&level=
2019 - https://www.sakugabooru.com/report/post_uploads?start_date=2019-01-01&end_date=2019-12-31&limit=29&level=
2020 - https://www.sakugabooru.com/report/post_uploads?start_date=2020-01-01&end_date=2020-12-31&limit=29&level=

You can also see what's popular by month:
https://sakuga.yshi.org/post/popular_by_month