1) If you want low maintenance and to not have to worry about rot at the bottom ends this is a great application for cellular PVC, aka Azek. Short of that use cypress or treated SYP at least for the wood closest to the ground.
2) hard to do and have it look right, but yes-- or see #1
3) Sure. I'd probably use a bracket something like the one in the link anchored with tapcons, expansion bolts, or bolts epoxied into your concrete, depending on the condition of the concrete, a pressure treated post, wrapped with cPVC.
4) sorry, don't know. It's not code legal (climbable and spaces too big) in the picture you posted, but would be fine at ground level on your porch.

Here is a link that might be useful: post support

1. Treated lumber 1x or 2x depends on how massive you want it to look.
2. It's treated so why not?
3. You'll have to drill the concrete and insert anchors, so , yes it is possible.
4. Google 'porch railings' and you can see different styles.

I would put PT 2x's on the front and back (with countersunk Timberlock screws from one to the other) and then wrap the post with cellular PVC boards. If the house design will tolerate it I would make the posts square.

You could also remove the concrete blocks and build whatever kind of post you liked.

I'd consider just removing the bricks and replacing with a fiberglass column.

There is PT wood that's treated for ground contact. If you go the wood option, use that.