Join our Discord!
The link to Prime32s 'More Monster Feats' under Extra Material in the Index got missed up from your edit today Osle.
So for example a green hag 2 who takes a level of sorcerer would count as having 3 levels of sorcerer(2+1) and gain the spell slots and spell known that a sorcerer gains when leveling from level 2 to 3, but not the spell slots and spell known that a sorcerer gets from level 1 to 2, He would get the familiar ability, but half-dragon levels wouldn't count for it.
The hag takes penalties to her physical statistics for aging, instead actually gaining +1 Strength, Dexterity and Constitution with each increase in age category, to a maximum of +1 per Annis Hag level. She ages as a human for the purpose of age categories, starting at adulthood (15+1d4 years old) and aging up past venerable age, but she will never die of old age (although she can always get uglier).