Question for Sudoku Nebula--does each region obey exactly one rule? So, for instance, a Clone shaded area can not contain only Evens or only Odds?
There is no restriction on a region taking up more than 1 rule. For example, the "Odd"-assigned region may end up having cells add up to 21.
But in the end, all the rules must be accounted for, in the exact number that was given in the IB, (Eg. 3 of Extra Regions, 2 of Clones ... and so on.)