Use primer first, and you will be fine. You need to pressure wash off if you try to strip, and not easy due to the enclosed area.

The easiest would be to prime and paint it over, but it will not look like natural wood. Otherwise, you will need to strip and sand, and this will not...

Armstrong Clark Black Walnut or TWP 1504 Black Walnut.

That looks internal. It may not come out. You can use a dark brown or black color stain to blend.

Yes.

What does it look like when wet with water?

Ready Seal is easy to strip. What stripper did you use? Did you brighten the deck after? The stripper will darken the wood internally, and the brighte...

Brighten after.

Concentrate most of the prep on the horizontal wood. Use a Deck Stripper and pressure washer to remove as much as possible. Let dry and spot sand as n...

Are you trying to remove all the solid stain so you can go semi-transparent? That will not be easy, as it will require lots of sanding/stripping if yo...

No need. Messmers is easy to strip.

The RAD Deck Stain Stripper and then Brightener: For the best IPE stains, see here:

Yes, strip and brighten, it will be easy:

Yes, spot strip as needed and then brighten all when done.

Cabot used to make great stains until they sold out to Zinser 15 years ago. Now they are crap. Look for a better brand.