Yes.

The correct product would be the TWP 100 Series for this. Clean and brighten the wood for the final prep before applying.

Strip it down back to harewood?

Thank you for the help!

Strip it all down is the best way to fix this.

Wait 48 hours after the rain to do the floors. As for the posts, it the rain did not harm the appearance, then no need to redo.

No matter what you have to remove the ZAR fist by stripping and or sanding. Once down to the bare wood, you can use any semi-transparent that you like...

Yes.

If the wood was stained before would the rust penetrate into the wood?