Idioms-SO AS TO + SO THAT + SUCH THAT + SO....THAT

Hi,

Can you please explain the usage and meaning of:

1) so that
2) so ....that
3) so as to
4) such that


Below is my understanding I had till now for the above mentioned idioms:

1) SO THAT is used to show the PURPOSE of something,

I brought chocolates today SO THAT I can sell them tomorrow.


2) SO....THAT is used to show degree

The water was SO hot THAT I couldn't wash my hands properly.


3) SO AS TO- This is one of the confusing idiom I have seen in GMAT. Sometimes OG says it is correct but in most questions it says this idiom is not correct.

I am really confused in this.

Till now I used to do below whenever I see this idiom:

SO that is preferable to SO AS TO

but when I was doing below mentioned question I didn't get it.



The Emperor Augustus, it appears, commissioned an idealized sculpture portrait, the features of which are
so unrealistic as to constitute what one scholar calls an "artificial face."

(A) so unrealistic as to constitute
(B) so unrealistic they constituted
(C) so unrealistic that they have constituted
(D) unrealistic enough so that they constitute




4)such that- don't know how/ where to use this.

Is it similar to SUCH....THAT ?


Please help!

Thanks,
Vishal