Necromancy: How cognizant would a recently deceased & raised ghoul, or zombie be? Could they speak, would they retain their abilities, knowledge? I would assume there are degrees of this based off the Necromancer's powers, but on the spectrum of "classic mindless shamble to passes as if they were still alive" whats the limit of necromancy? And I assume free-will is a thing of the living? Would they be able to resist the orders of the person who raised them?

There aren't hard rules on the subject, except that PC necromancers don't typically have the power to raise an intelligent undead..although they may accidentally summon a crypt ghoul (see the From the Grave print on demand ). GM necromancers can do whatever they want, as they're not bound by any hard rules. There is discusson on necromancers in the wizards and priest books.

Creature guide: "

Ever since the time of Nagash, the first and greatest necromancer
who unlocked the secrets of life and death thousands of years ago
in the ancient realm of Nehekhara, the dead have risen from their
graves at the behest of evil sorcerers schooled in the arts of necromancy

or by other dark means.

..

Some undead still retain the power of free will and are able to think
and scheme through the shadowy mists of undeath. Most, however,
lurk mindlessly in the shadows until stirred by the activities of mortals.
In their anguished state they will lash out and attack anything
that disturbs their fitful sleep.
The mindless undead can be awoken and forced to do the bidding
of the strong-willed undead such as vampires or necromancers.
Wielding a dark magic that goes back to the time of the ancient
desert kingdom of Khemri, necromancers strive for immortality
or simply seek control of the dead in order to advance their earthly
power."

Demonic familiar: I heard the 2nd edition had some guidance on this but I'm not familiar (see what I did there) with those rules, and I'm specifically looking to have a demonic familiar rather than an animal or automaton. If a Chaos sorcerer summoned a demon familiar could he talk through it? Could it (or he) cast his spells in his absence? Would it need to retain a certain proximity?

There are no hard rules on this as it is an NPC thing. Imps are the monster category for this sort of thing.

PCs have some spells that I recall allow a person to talk/view through an object, but they are limited in time and scope.

I'd house rule that a Chaos Sorcerer couldn't just use his familiar as some kind of "duplicate" of himself. That would be like saying, "Oh, the soldier in my group can cast my spells, even though I'm not really even around."

..