6. No it is not equilateral because a. All the angles should be congruent (60) and as we can tell, they are not, and b. you should never assume measurements.
8. GF is the longest because the angle for that side (GFH) is smaller than the others, so it means it has a longer side.
Your answer for 9 is wrong. The answer is yes because the largest angle = the largest side.
10. AC because largest angle = largest side
11. Literally the same thing as 9 and 10. Largest angle = largest side
