This is an unrated window
Yes the picture shows it with a screen that comes with it
I have 3 in my steel building that I installed from the outside by cutting off top and bottom nailer and sliding sides behind panels and screwing. A bead of silicone around both sides and the look good.
Yes. I bought for my cabin
no opening must be 36 x 36 inches
Same dimensions , brown by Jeld Wen, starts at like $140 or so...make$ white look pretty good...
We suggest not removing the J channel
No. You would just have to leave one side open and rig something up that might work. But there is no attachment or offer to purchase an insert that the vent can go through. The window is nice enough, but came dented, so every time I open/close it it catches and I have to lift it up over the dent. I didn't notice this before I installed it, so if you do buy it check it out good before you install it, as it could have been returned and replaced.
The rough opening is 24x24.