Past Perfect question forms with 'before' etc

Solution 1:

I'll address one question:

'Had you read the instructions before you turned the device on?' looks fine.

'Did you read the instructions before you turned the device on?' looks fine.

But notice the 'looks fine' rather than 'sounds fine'.

If I've just caused $500 worth of damage, my agitation will be less amplified by the first variant; use of do (did you ...) sounds rather more confrontational. Of course, intonation and non-verbal communication may be even more confrontational.

So the two variants here are both grammatically fine, mean the same thing, but the first variant might be chosen to avoid adding too much insult to injury.