Can you make feet into claws?
Monstrous Extremities: "You can choose from a tentacle, a hoof, or a wing."
Can you attack with the natural attacks alone as primary attacks?
Monstrous Extremities: "they do act as natural weapons of the appropriate type, and the subject can use them to make secondary attacks while making attacks with weapons as a full-attack action."
Natural Attacks: "If a creature has only one natural attack, it is always made using the creature's full base attack bonus and adds 1-1/2 the creature's Strength bonus on damage rolls."
So if the creature has no natural attacks, then it gets a Monstrous Extremity, then that is its only natural attack, and thus it acts as Primary, unless it also makes attacks with manufactured weapons.
Can the now tentacle limbs grasp or manipulate object?
Monstrous Extremities: "The subject cannot hold a weapon or use any item that would ordinarily fit into the slot of the changed extremity."
I would allow a tentacle to manipulate objects within reason.
Would the attacks with wings be considered claw attacks?
No, they're wing attacks. Claws are claws.
Check out the Table.
I am thinking pterodactyl wings here.
If you mean Pteranodon, it doesn't actually have a wing attack. If it did, since the Pteranodon is Large, it would deal 1d6 Bludgeoning damage.
With a one minute casting time, opportunity to use it offensively seems pretty limited.