Hey guys,

the char-level which rerolls, and the item-level of the diadem doesn't matter right?

(I only want to know for diadems, for tiaras or so the clvl does matter)

It doesn't matter indeed, unless you want 2 sockets.

they roll from the maximum list of affixes at any ilvl due to their qlvl 85. They can be imbued by level 8 chars or rerolled by level 1 chars and the item level doesn't matter
but as feanur said, max sockets are still limited by ilvl. It can't have more than 1 socket from ilvl 1-24, 2 sockets from 25-39, and 3 sockets level 40+, though that doesn't matter for rares.
so you want a level 25+ char.

Okey, thanks guys!
But for imbue lvl 8 is fine right? since they drop with high enough ilvl i guess

when you imbue items, ilvl is set to clvl+4, so it wouldn't be able to spawn with 2 sockets