> By the way, what is the parent language of Old Norse

Why, Even Older Norse of course! :)

It's usually called Proto-Norse. That, in turn, is a descendant
of Proto-Germanic which is a descendant of Proto-Indo-European.

Something like that. A handful of inscriptions are preserved
in Proto-Norse. From those and comparative linguistics we have
a pretty solid idea of what the language looked like.

Kveðja,
Haukur