nut

Hi, I’m trying to replace an old kitchen faucet as I already received a new one, but I have no clue how to remove the nut and pieces holding it in place. I don’t know the brand or how to even look on getting it off.

I'm switching out the toilet water feed and I see some beginnings of corrosion on the lower nut . It was only installed 2 years ago...to protect the newer piece can antiseize lubricant be used to deter corrosion?

This is under a bathroom sink and is too thin to grab with my basin wrench, and too close to the edge as well. I also tried tapping one of the slots with a long screwdriver and hammer. Is there a special tool or workaround for this? Photo enclosed. Thanks!