[ss3964spd]

A: Any tape applied must be done before Redgard.

B: Water will just sit in the low spot, it won't filter thru the Redgard - unless there is a hole in it. Any accumulated water will eventually dry out, depending on how often the shower is used.

C: Yes, you'll want to stay off the Redgard to avoid damaging it. I think I'd opt for applying the RG to the floor after you've tiled the walls.

D: I believe I've read here that the PEI rating isn't used anymore, though some manufacturers still invoke it. Regardless, any tile that is rated as a floor tile should be fine.

F: Yes, a lighter grout color is more likely to appear dirty faster. But as this is a shower it won't be subject to as much dirt and grime as, say, a kitchen floor would be. I'd use whatever color you, or Mrs. Fabin, would like. IMO, natch.