I see no problem with that, but cedar does have a smell you are going to have to consider.
Cedar is a very good outdoor wood, not even sure I would put a clear coat on it, unless you just like the “shinny look.”
Cedar is a very good out door wood, I think as long as the board is dry and flat when you make them, it should stay that way for a long time.
It depends on the drying conditions and how wet the wood is to start with.
There are better woods for post, but cedar should do it for you.
Would not recommend, wood is too soft & will damage easily.
My friend builds beautiful strip kayaks made of cedar and likes working with the wood. You will need to rip this board into 3/4 x 1/4 for your project...however be sure to check your project special specs and instruction. Good luck
This can be used for a table, it does not need to be sealed.