It is opaque, not semi-transparent in appearance. Behr lies about their opacity. You will need a solid stain pain strip and sanding to get it all off:...

it has to be a .jpg .png. or similar file.

1. No, it does not remove solid stains. 2. For 2 coats applied on 300 sq feet, you will need closer to 3 gallons. 2 Gallons would be enough for 1 co...

1. What they applied is not semi-transparent. Either they applied the wrong stain, or the manufacturer "lied" about its opacity, as it clearly looks l...

The Helmsman is interior only and will have no UV or water protection for exterior wood.

What you have is opaque or a solid stain. The easiest is to apply a darker solid stain over it. Look at Restore A Deck Solid Stain in the Brown Oak or...

I doubt it. If bad, it crystalizes in chunks.

If you can, sand off the helmsman and use the RAD stain. Use 60-80 grit paper.

Yes, to both.

Maybe, but it is about having a solid foundation for recoating. We would do the strip but up to you.

It needs to be outside to properly cure and dry. Put it out there, and hopefully, it will all be good in a day or two.

See this for recoating with a solid stain:

No, you cannot add a clear coat over a deck stain. It will peel if you do this. Behr, BTW is a very poor stain. It will peel most likely. Terrible rev...

Is this inside or outside?

You cannot coat anything over the Helmsman. You would have to remove that first.