Are they, both sentences, grammatically and semantically acceptable?
- Why do you not give him your flesh and your bones?
- Why do not you give him your flesh and your bones?
This is a very simple example of subject–auxiliary inversion, and it is required in most interrogative sentences in English. The subject and the auxiliary verb appear in the reverse of the order in which they would appear in a declarative.
Consider the following declarative version of your interrogative:
YouSUBJECT doAUXILIARY notNEGATIVE give him your flesh and your bones.
In your interrogative version, the presence of the auxiliary verb do causes subject–auxiliary inversion to take place. In negated questions like this one, the negating word not should appear after the subject, not after the auxiliary:
Why doAUXILIARY youSUBJECT notNEGATIVE give him your flesh and your bones?
Note that the negating word can also appear attached to the auxiliary in the form of the contraction don't:
Why don't AUXILIARY + NEGATIVE youSUBJECT give him your flesh and your bones?
Only the first one is grammatically acceptable.
To clear up some potential confusion, here's a clarification on contracted and non-contracted sentence structure. Here is the sentence with a contraction:
Why don't you give him your flesh and your bones?
while this is not contracted:
Why do you not give him your flesh and your bones?
however, it is not this:
Why do not you...
Don't contracts the do and not, and even though the shortened words appear next to each other when contracted, the subject of the sentence (in this case, you) must go between the do and not.