I doubt that it is kiln dried at all. Also if I was going to stain a piece of wood I would start with an unstained product. If it has already accepted stain how much of your stain will it accept? The answer is not much. You might want to think about what you want the wood to do or not do and what you want it to look like. You may end up using an oil base paint if it works better with the stain. Do your research.
Unless it is wet, very heavy, it is dry enough. There is no need for sealer it is PT it should last 20 years in the ground. If you do not use concrete you can anchor the post with tamped gravel.
Already is pressure treated. Should last at least 25 years.
As per Bob Villa: Yes, you can paint it when it is dry. This can (and probably will) take several weeks even months. If it feels dry put a couple of drops of water on a horizontal surface. If it beads up, it is too wet. If it soaks in quickly it is probably ready. One coat of primer then two coats of exterior paint.
I have never painted any of my pressure treated wood. That said, I know the paint would extend the life of the wood, but I prefer the natural look of the wood. That is why I love these latest pressure-treated timbers. The dark color is awesome. We shall see how long it lasts.
Impossible... Each post holds a different amount of moisture, they range from pick it up like a suitcase to, "JEEZZZOOOO!!!"
There are different "Use Categories" depending on the use, termites like none of them. Take your reading glasses and read the tag stapled to the end to confirm... it will tell you which kind of protection the particular treatment provides... I believe this particular one is UC4, for ground contact UC3 is NOT ground contact and UC2 is for interior damp use
This product can be painted.
I don't see why not. I used pressure treated timbers on two raised beds and we have had zero issues.
I rented the van and the 10 foot long 4 in. x 4 in. fit in nicely. If you use the truck you would have to tie down as they would stick out the back.