I see Auto Zone, Advance, and others have a selection of gasoline water
absorbent/breakdown stuff. Some says words to the effect of "for 4 cycle
use".

I know Boat US and West Marine sell some that does state it's for 2 cycle
use. And, lo and behold, it's about double the price.

The question I have is twofold:

1. Can I use the stuff in my 2 cycle o/b that says "for 4 cycle use",
without harm?

2. Should I use only stuff that says "for two cycle use"?