请教柯帕斯英语网的专家：

My journey home from school is nothing special. The train’s always busy but I usually find a seat and start reading or texting my friends, making sure, like everyone else, not to look at other people.

But last Tuesday was different. I was happily listening to some new music when the train suddenly stopped. This wasn’t unusual and I didn’t think anything of it. Then after about five minutes, I noticed people were starting to get a bit angry. Fifteen minutes later, people started getting angrier. The longer the train stood still, the angrier people became until finally the announcement came: “We are sorry to announce that this train is delayed.”

That seemed to calm people down and so we all went back to what we were doing before, but soon there was another announcement: we were going to be there for a long time--- a train had broken down in front of us. There was a loud sigh throughout the carriage but then something unexpected happened: complete strangers started talking to each other. I started chatting to a couple of young tourists sitting opposite me. They were from Spain and they were travelling around the UK so I recommended some places they should visit. Next, I really surprised myself by starting a conversation with a businesswoman. She was going to take three months off work to climb Qomolangma. It was great talking to her. Then I decided to get up and go for a walk down the train. I met a woman who had been a student at my school seven years ago and knew lots of my teachers.

While we were talking, we heard there was a patient in another part of the train who needed help, and the woman from my school jumped into action. It turned out she was a nurse, and when she came back she was welcome as a hero.

Then, after two and a half hours, we started moving again. Everyone clapped and cheered and some people, complete strangers three hours before, even hugged. I’ll never forget the day the train stopped and people started talking.

1)  I met a woman who had been a student at my school seven years ago - ago 是否错误？要改成before ?

2)  complete strangers three hours before, even hugged. - before通常要和完成时连用，这里的before是什么用法，为什么这里没有和完成时连用呢？