3D referencing, Use SUMPRODUCT to "SUMIF" multiple columns

There are a few common formulas which I use when it comes to reporting as per below

1) 3D referencing ~ Allows one to sum cells in all sheets residing between 2 anchoring sheets. There is the flexibility of shifting sheets in (or out) of the the anchor points if one should decide that additional sheets should be included into the summary. E.g below screenshot

2) SUMIF involving multiple columns through SUMPRODUCT: Using Sumproduct to perform a "sumif" which involves multiple columns as per below .