Question

For+一段时间可以用于一般过去时吗

Answer 1

可以，依句子的意思而定。
ep: I felt sorry to hear that his sister passed away after having fought against cancer for three years.
现在完成时是表示过去发生的动作一直持续到现在，而“去世”这一动词显然不能持续。所以我认为for+时间段 大多数时候可作为现完的标志，但并不绝对。

Answer 2

可以：My mother had to stay in the hospital for a month.
母亲在医院里待了一个月。

Answer 3

过去完成时