For #3, The Renishaw routines need a place to store settings. e.g. probe tip diameter. They ask you to provide them a range of G code variable in the 500-999 range. These variables get saved across machine restarts. But many G code programmers also use this range. So they ask the person installing the probe routines where these settings should reside so as not to conflict with other settings. Finding this information will be like finding a needle in a haystack.
To convert the code, you must have a full understanding of two machines!! The machine where the code came from AND Mach (Fanuc 21i). For example, I don't know what #50601 is!!! Further more, why would it be EQ 1? These are the questions will come up and they will have to be answered by the person converting the code. #26 is, and always will be, a local variable that has the contents of the Z word. #26 is pretty much universal.
As for the list of G code variables, the Fanuc 21i parameter manual has every one on them listed. e.g. #5061 is the X probe position (skip position). There is also lots of information on the net such as:
http://www.machinetoolhelp.com/Applications/macro/macro_variables.html We patterned after a Fanuc so as to be compatible. We don't implement every one of their parameters because some just don't pertain to our system at all (like ROM option bits, etc...). But the ones for probing are implemented precisely so that the Renishaw Fanuc probing routines will work.
As for documentation, we just haven't done it. Why? There is plenty of Fanuc documentation out there and we would be just duplicating that anyway. Whole books have been written on the subject. One great source for Macro B programming is Peter Smid's book "Fanuc CNC Custom Macros".
Steve
Steve