Little off topic: I'm surprised to see the word Grandmother with a capital G?
Not a native English speaker though.
It's because "Grandmother" is the name of the speaker's grandmother. I called my grandmother "Gamma" :-)
Its because it refers to a specific grandmother!
It's possibly some reference that at least we two didn't understand
det var när farmor fortfarande levde. är det okej?
That would rather be ”when Grandmother was still alive”.
Why is levde fortfarande not accepted here?
That's not an accepted word order. Swedish wants the fortfarande before the verb here (but adverbs are tricky, sorry).
In that case, why is "min kusin levde fortfarande" the target answer for one of the other questions in this topic?
Adverbs will generally prefer to come after the verb in a main clause. But they will generally switch places to come before the verb in a subclause.
Det var [=main clause] medan farmor fortfarande levde [=subclause].
So they behave in the same way as inte?
inte is an adverb!
Unfortunately I don't get the point here.
Is det more
Smör tillverkades hemma medan farmor fortfarande levde.
Vi ringde läkaren medan farmor fortfarande levde.
So is a period in the past meant here or a point of time in the past?
Adverb is before verb because it is subclause? Doesn't it