I'll deal with the ambiguity in the question by providing options.
What if a creature such as you propose evolved characteristics found in more primitive Earth creatures, how about
"What if: It can impale it's prey with a paralysing venomous barb that comes from the same orifice that it poop through."
For a "Digestive System Within Limbs"- (plural) your creature design might need a combination of features many of which are already found in nature.
- Since it's not an amoeba you're going to need:
Extracellular digestion is a process in which saprobionts feed by
secreting enzymes through the cell membrane onto the food.
Sure, this is most commonly found in fungi and don't houseflies start digesting their food before they eat it?
Humans use extracellular digestion when they eat.
Their teeth grind the food, enzymes and acid in the stomach liquefy
it, and additional enzymes in the small intestine break the food down
into parts their cells can use.
- Well, but a digestive system in the hands and or feet, how would that look?
An Armed Proboscis
the proboscis exits from an ... orifice. A typical member of this
class has a ... calcareous barb, with which the animal stabs the prey
many times to inject toxins and digestive secretions, after ...
digestion, its tissues are sucked in ... Either side of the active
(barb) are sacs containing back-up (barbs) to replace the active one
as ... an active one is lost.
Ribon Worms can do it and here's the phenominal speed of it.
Annoyingly I'm not able to Embed a Youtube video, so here's the link:
- Hellava handshake! But your prey is not going to like that very much, they'll kick up a
The ... tooth is loaded with venom from the venom bulb and ... is
fired from the proboscis into the prey by a powerful muscular
contraction. The venom paralyzes ... almost instantly
If each of your creature's fingers behaved like the guts of that thing, (IE. Digestive System Within Limbs - plural) then at a pleasant soiree it could just casually feed on hotdogs, burritos, crisps as it went around chatting, or equaly without a care continue a conversation whilst it fed on a person or defended itself from attack.
- Alternativley sticking more closely to your chosen three limbed morphology, with the two fore-limbs and the foot, it could turn its (Single) gut inside out like a hydra:
Leaving your creation's mouth free for kissing/light opera/chat - whatever.
While it's Anus digests it's paralysed prey at it's feet/foot. :)