Excel Formula and Guidance

This is not supposed to be an exhaustive live of excel formulas for that I would suggest visiting https://exceljet.net/formulas but rather key formulae/functions that could prove useful for your work in Planning and Insight.

Other notable sources of information on excel.

https://www.spreadsheetweb.com/how-to-count-values-between-two-dates/

https://www.extendoffice.com/excel.html

Averageif between Dates
Sum values between two given dates of a data range, to average numbers between two dates also can be solved by using some formulas

Countif Dates
A quick and easy way to count between dates is by using the COUNTIFS formula, create formula-based filters.

Count by Week Number
As it sounds, but an explanation of how to use this.

Count unique values Excel
Using sumproduct and countif to gain the number of unique values within a range.

Index Match
The INDEX function can be used alone, but nesting the MATCH function inside it creates an advanced lookup.