1. When the monkey is opening its mouth, how come is opening so far without any anomalies? Did you use a deformer?
no deformer. just points weighted to a jaw joint. https://gyazo.com/7a6236f2ceb1069e8e9b065de183b77c
2. I understand that the tongue "is a tracer made out of animated nulls to form a spline, then i just spline wrapped the tongue model onto the tracer". When it curls from man to monkey, how does it get the sort of liquid effect? is it using the Metaball.
i t is again splines in a cloner spline wrapped onto the same spline as the tongue, just offset a little. because of the flat simple colour shading it just looks like it's one unified thing with the tongue, but it's not. just two separate things that look like one.
3. Also when the monkey changes to man, the tongue has something black on it. Is it still splines with tracer object and metaball?
yes.
4. When the man is changing to monkey, how do the hands break up from the character and extend? Are you using a Boole?
yes.
5. Also before the morph from man to monkey you have the hand moving around and some blue liquid particles. Are those particles or Cloner?
those are particles, added in post. but you could do that also with particles in c4d, either native particle system or x-particles.