The order of validation rules within a cell is important, as some rules may not function correctly—or at all—if applied in the wrong sequence.
It's important to note that, regardless of the order listed below, not all rules are compatible or may function together. This is simply a comprehensive list to help ensure they work correctly if used in combination.
Here is the order for the different validation rules:
readonly and/or optional and/or hidden and/or freeze
roundup[...] or rounddown[...]
Need to go with a "Formula"
Formulas and validity[...]
Formulas would be for calculations or timespans between parentheses
validity[...] would be for the targeted fields and/or columns between parentheses for a validation
Fills grid with [...]
Updated by [...]
Show when [...] is [...]
Copy [...] when [...]
SET [...] when [...]
Invalid when [...] or Invalid when [...] if [...]