I'm 5'9, 165 pounds. A) What would happen if a giant snake came into my bedroom? B) What part of my body would pass it's mouth before it had to stop? IE Waist, thighs, knees, etc. C) What if it started at my feet? How far up could it go?

Guess it depends on how big the snake is.
I know a bit about snakes and I've never seen one attempt to swallow something it couldn't.
Part of the constriction process is tenderizing the prey by crushing bones, etc. It seems like the only thing that wouldn't pretty easilly deconstruct would be the pelvic girdle. That, I would guess, the snake could break into a couple of pieces for his or her swallowing convenience.
I suggest we put on your tombstone (alas, it will be a closed casket funeral service) "Something He Disagreed with Ate Him"

A) Just run, surely you're faster or try get anything sharp.

B) Considered you're caught, it starts with your legs, try separate your legas apart so he can only get only one leg, then it will stuck highest at your thigh.

C) Same as B. I don't want to imagine it starts with your head, If so, then you better not worry about where it will stuck already because you're finished.

Why you ask this Q anyway?

It would'nt start at your feet because it would gawk at your thick yellowy toenails..........It would realize you are damaged goods so it would move on.........Quick...better go save your sister.

If this Giant snake is hungry he'll attempt to constrict you till your unconscious or stop moving or dead assuming he starts head first me might have initial issues with stretching his jaws so wide and so abruptly but feet first and its a gradually widening process so he has a good chance of swallowing you now big snakes always go that little bit further and swallow food whole so since your being swallowed your food and your food so your going o be swallowed whole not halfway or at the knees all of you or else he'll just spit you out so basically summatise

1. Feet first theres a significantly high chance of you being completly swallowed

2.The snake will either swallow you whole or spit you out no holding on to meals for later im afraid

3.and finally if the snake came into your room he is either hunting, trying to get warm, lost, or worst of all determined to swallow you RUN!!! before he catches you.

They always start head first and spit out the shoes.
Shoulders might be a problem.

a anaconda would crush your bones into jelly and fold you up like a jack knife and swallow you in one gulp and move on to the next house.

I think the question is, why are you off your meds?

I'm getting swollered', by boa constricator
I'm getting swollered', by boa constricator
I'M GETTIN' SWOLLERED', BY BOA CONSTRICTOR
And I don't like snakes one bit

What'a ya know
He swollered' my toe

Oh gee
He's up to my knee

Oh my
He's up to my thigh

Oh yummy!
He's up to my tummy

Oh fiddle
He's up to my middle

Oh glum
He's mashing my lungs

(spoken)
Now look here snake!
I don't look good with this long tail on me
That's about all I can say snake, except give me a break snake!
My torsoe's cold and it's starting to mold
Boa Constrictor...How much can you hold?

(singing)
Oh Yes
He's up to my chest
Oh heck
He's up to my neck
Nearly all-len
He's up to my chin
Oh dread
He's swollered' my head

SNAKE Burps..."Excuse me."

Boa Constrictor Song by Peter, Paul & Mary

you have the desire to be eaten whole.. what a novel fetish