1,错的,因为比较是平行结构,as前后的内容应该一致,应该是you are not as beautiful as you were twenty years ago
2.对吧
3.错的,应该是this year is a lot colder than last year
4.对的
5.错,it is very hard to recite every text
6..of own 改成of his own
7.In the accident last year,he became blind