Did you install the rack by attaching to studs or just drywall? Wine is heavy..any problems with the racks pulling out of drywall?

I attached one side to a stud (the side where the bottom of the bottle would go) and the other just to drywall anchors. Have had no issues with the weight. I installed three sets - all were installed the same and all are holding up very well.

Are the rods holding the bottles equally spaced on each side?

The rods come separate. You hang them up and make sure you use a level on the top and on the bottom. So there are two rods and you space them how you desire. I just went by the directions. It was very easy. You do need a level and of course a drill and a screwdriver.

What is the depth of the 18 rack?I know it's about two bottles deep, but I have a weird space and want to make sure it won't get whacked with a door:)

The depth of the 18 bottle rack (double deep) is 8.5".

Can the direction of the bottle be reversed?

The only way that the direction of the bottles can be reversed is to take the wine rack off the wall and swap the two brackets and remount them so the bottles face the opposite direction. If it is the initial install, and you already know which direction you want the bottles to face, it can be done during installation.