No on the primer unless the brand od solid stain you are using specifically says to use one.

Yes, you will need to wait and prep:

No need to sand. Prep with the Restore A Deck Stripper/Brightener kit with pressure washing. The stain will come off easily and prep with a nice even ...

After you finish the prep, let the wood dry for a few days. Stain withing 2 weeks of the prep with Armstrong Clark or Restore A Deck Wood Stains.

I live in MO and I have a deck that is 14 years old but was never stained. It is on the north side of the house and some of it never gets direct sun ...

Semi-transparent. Either oil or water-based as long as it is one of the top 6.

Should I use Semi Transparent or Solid stain, also should I use oil based or water based stain.

Yes, that is possible.

Thank You for the quick response. I used sodium hydroxide beads to clean this, mixed at 1 0unce per gallon of water, with a soap surfactant added as w...

See this for tips:

The Defy Extreme would work well for this. You will need to clean and brighten all the wood for the prep.