1 Pyrocat HD..and I have tried most of them. It is the easiest tanning developer I have used with no uneven stain at all.
2 not with Pyrocat HD, depending ont he formula you are using the tubes affect the result to a greater or lesser degree.
3 Perhaps! if you get pyro on the grout between the tiles you will be sent to the dog house for eternity.....If you use the BTZS tubes it is easier to control splashing, so just be careful.
4 Of course...!