1.We have lived here since three years ago.
2.It was ten o'clock when I got home.
3.When I got home,it was exactly 10 o'clock.
4.I only knew the truth after a period of time.呃，是It开头的句型诶。。1. It has been three years since we lived here.4. It's been some time after I knew the truth. 希望对你有启发