There are two types of validations at list level:
Column validation: Here you could validate the values for a particular field. You can configure this from the
edit columnpage – with different messages for different columns.
Item validation: You need to use this when you have a rule that requires values of multiple columns. You can configure this from list settings -> validation settings.
However you cannot have two item validations configured.
So if you have multiple rules that require more than one column value to validate against, I would suggest two alternatives:
Place a content editor web part on top of your
new itemform, and write these rules in plain text. So when any validation fails, users can read all these rules.
newpage, and then based on the validation errors, you can give different alerts on screen.