I had a metal finishing shop in the UK for 15 years - Precision Surface Preparation.
Metal polishing, all disciplines, and wet and dry bead blasting.
The plating itself was farmed out, as was the chemical stripping of old plating, prior to us doing all the prep work. Plating is only as good as the prep work. Labour intensive - it's where most of the money goes.
In answer to your questions;
# zinc and nickel/chrome plating are very very different processes.
# i have no experience with home hobby kits.
# I highly doubt you will be able to plate or replate a m/c frame with such a kit.
# No, nickel goes on before chrome.
Triple chrome plate is polish, copper, polish, nickel, polish, chrome.
# Doubtfull, and if you did/could, it will look a mess, see above.