a. Will this stuff work on dirty corny kegs with cold water?
yes. (Hot water just works really really well when I've used it on smaller parts that I can get to the tap, but with kegs, carboys, kettles, I use the hose.
b. If so, how many times can I use the same solution? (I have many kegs)
I reuse within a 10-20 min window. Not sure if this is based on science but it's what I've done.
c. How long does it to clean a keg if soaking?
10-20, I add then scrub minutes after.
d. Is it safe on copper and stainless?
e. is there anything special I need to know?
cleaning is the hardest part that I wish someone else would do.