Past simple vs Past Perfect with after, before

Ex. I went to school after I finished my homework.
After I had finished my homework, I went to school.

I went to bed before my parents came home.
I went to bed before my parents had come home.

Are the above sentences all academically acceptable in terms of grammar?

Can we use simple past if it is clear that one comes before or after another?

The rule is a bit unclear about this:

If the Past Perfect action did occur at a specific time, the Simple Past can be used instead of the Past Perfect when "before" or "after" is used in the sentence. The words "before" and "after" actually tell you what happens first, so the Past Perfect is optional. For this reason, both sentences below are correct.

Examples:

She had visited her Japanese relatives once in 1993 before she moved in with them in 1996.
She visited her Japanese relatives once in 1993 before she moved in with them in 1996.

HOWEVER

If the Past Perfect is not referring to an action at a specific time, Past Perfect is not optional. Compare the examples below. Here Past Perfect is referring to a lack of experience rather than an action at a specific time. For this reason, Simple Past cannot be used.

Examples:

She never saw a bear before she moved to Alaska. Not Correct
She had never seen a bear before she moved to Alaska. Correct

Does this "specific time" mean that as long as we can clearly see what comes before or after it's okay to use simple past? Or does it mean that we must have a number specific time?

Thanks!