use present tense to express future in some subordinate clause

Question

In the two following sentences, it is correct to use present tense to express the future

I hope they are working hard tonight.

Students who graduate three years later will work in that factory.

But if I change the tense of main clauses to the past tense, it can be used in the same way?

I hoped they were working hard at that night.

After the college entrance examination, students who graduated three years later would work in that factory.

Can these two subordinate clauses express the past future?

Because I know if you change "If it rains,(tomorrow will rain) I won't go outside."

to the past"If it rained, I wouldn't go outside" means"At that time, it already rained, and I wouldn't go outside"

like: She had had dinner before her father left.(father left?) She had had dinner before her father was going to leave(father left?)

But if we say : She have had dinner before her father leaves(This one means her father will leave)

Thanks a lot!

Answer 1

Your tenses are fine. I will rewrite your sentences just a little bit to make them more natural sounding to my ear.

I hoped they were working hard

Students who graduated three years after taking the college entrance examination would work in that factory.

The second sentence sounds a little weird, but I've seen sentences like this in the beginning of biographies. It sounds like a foreshadowing.