Subpart counter should be 0-indexed

One of 0- or 1-indexing should be the default - both in Rails and in TeX.
We have chosen 0-indexing
Add explanatory diagram + corrected error in version 0
New macro - \setVersionTriggers[1] - defined to trigger version switching

The macro is written along with \setAuthor and provided the list of
subpart indices (0-indexed) after which version triggering should happen
Add a blank page even for a one-pager
Remove \setcounter{rolldice}{0}

Was overriding the last set version
eliminated \nextpg from multi-part questions