I'm working on a bioweapon created by an extraterrestrial agent. The being is 2.5 m tall, humanoid, digitigrade, intelligent and mostly predatory. However, it does not require water, food or oxygen to survive (let's say it is sustained by "bullshynthesis"), though it can do so to get raw materials it uses for making offensive weapons(quills, claws, etc), and hunts solely to spend excess energy and for sport. the creature has a few cemented traits, including the ability to grow and undo specific structures (such as claws, plates for teeth, extra limbs, a tail, aquatic adaptations and others).
The main issue comes with three qualities: its lower jaw splits to reveal a spinneret organ, its limbs are capable of stretching to a certain degree and it can squeeze through spaces its body technically shouldn't.
The being is meant to have this many traits to be able to hunt no matter the environment (I'll admit it's quite the Frankenstein of various animal traits), but I'm mostly sure this three last qualities appear not to be in line with the majority. Is there a way to get them to function properly? How could they work, if at all?
Edit: I pretty much remade the question, after realizing I wasn't being specific enough and it sounded like just a xenomorph with some new parts stitched to it. The creature has an appearance that indicates heavy influence or theropod and avian traits in its biology.