Okay Gents, another question or 3!

I am replacing my fence around my garden this year as we have many critters that love veggies. Currently have a 3 foot welded wire fence set on t-posts which has done pretty well for the past ten years. But am looking to spruce it up a bit. Mainly because my wood corner posts have rotted some.

I am looking to put in a 2 rail post and board fence 3 feet above ground, then attach new welded wire with a face plate. Post spacing will be 10 feet on center, and rails will either be 1x6 cedar boards or 5/4 x 6 deck boards.

Questions:
1. Since I am using post and board, do I need to brace the corners (except of course where the gate will be, which I will brace).
2. Will a 4x4 buried 1 foot deep with gravel and concrete mix be deep enough for the posts? It's not likely to have a lot of tension with the wire fence, or have wind load since it is a post and rail. Buying an 8' 4x4 allows me to cut them in half for this purpose.
3. Should I use cedar or deck boards for a 10 foot run between posts? My thinking is the 5/4 deck board so they won't bow over time.

Thanks for your advice!