1.Not eating for a week is a really amazing experience.
2.Not having eaten for a week is a really amzing experience.
3.Having known him for 20 years is the reason I trust him.
4.Knowing him for 20 years is the reason I trusted him.
请教老师第1,2句是对的而且意思一样,第3句是对的,第4句不对,我的判断对吗?