You are right that the past perfect is generally used to refer to an action that took place before the current point in a narrative about the past. For example:
By the time that I arrived at the station, the train had already left.
However, in time clauses with before it is indeed possible to use the past perfect to refer to an action that took place after the current point.
Swan in Practical English Usage (p100) has the sentence:
He went out before I had finished my sentence. (= before the moment
when I had completed my sentence.)
Note that in sentences like the last, a past perfect tense can refer
to a time later than the action of the main verb. This is unusual.
This ngram (before I had a chance, before I'd had a chance) is evidence for Swan's contention that the past perfect tense in the before-clause is unusual.
Nevertheless, it is easy to find numerous authentic examples via Google search (and see the Cambridge Grammar of English example below):
It was over before I'd had a chance to tell him enough times how much
It caused the cows to quit the feed before I'd had a chance to see all
Before I'd had a chance to DJ, I was playing live sets with my
I was already in love with this beer before I'd had a taste.
Before I'd had lessons with Wendy I had no confidence driving.
He threw out new ideas before I'd had time to absorb his previous
As to your second question, you can indeed use the past simple in both clauses. As Parrott in Grammar for English Language Teachers (p389) states in his section on Tense and time conjunctions:
After and before contain precise information about the sequence of events and so we don't need to rely on the tenses to provide this
information. We can use the past simple tense in both clauses.
- Your daughter left before you woke up.
The Cambridge Grammar of English (p60) provides a reason, why the past perfect (as opposed to the simple past) may nevertheless be preferred:
- He died in hospital. And before he'd gone into hospital, he kept saying to my mother ... .
The perfect aspect versions stress the completion of the event in the
before-clause and a break in time between the events in the two clauses. The present simple or past simple suggest a closer connection
between the two clauses.