Solid Hardwood, Engineered and Laminate Flooring - Brazilian Cherry Question

We had just had Brazilian Cherry Hardwood Floors installed less than three months ago. We are having a few issues with the floor and would like to know if these are normal or if it is something we should pursue further with our installer.
Firstly, we understood that the floor would darken with age, however, it has already darkened significantly in such a short amount of time. Is this normal?
Secondly, some of the stair treads creak. We told our installer about them and he didn't seem too eager to fix it, he suggested giving it some time. Well the creaking has continued along with additional stairs now creaking. Is this something he is able to and should fix? If so, how difficult is it to do?
Lastly, the finish bothers me, it looks uneven. I understand that sealer was put on and two coats of polyurethane (semi-gloss). As you scan the floor it is evident that there are quite a few uneven areas...some areas look dry and rough some look smooth. This is throughout the floor. I was wondering if another coat of poly was needed or was the job just not done properly.
Any feedback would be greatly appreciated.

The creaking is going to keep happening. Not sure how to fix it, but if it did not creak before, and it does now, it sounds like an install issue.
Not sure about finishes...sorry.
The floor darkened just fine it sounds.

Firstly, we understood that the floor would darken with age, however, it has already darkened significantly in such a short amount of time. Is this normal?

I agree with florcraft on this one. It will depend on the amount of light it gets.

How many coats of finish were applied?

We have heavy heavy U.V. light up here that lasts up to 19 hours a day during the summer, so our cherries darken fast!