Filtering the Native SQL Question

I have a created a Variable "Reporting Cutoff date". Now this variable is used to check the customer start date and end date (for example i want to count number of new customers between it).

I want to set it as Field filter, is it possible to use it to connect to two different fields. If not, what would be the alternative?

Can't you add 2 filters if you want to use the information of 2 fields

I wanted to minimize the number of inputs.

It leads me to second question - when we add a filter to dashboard, do we have an option to add a filter like "On or after" / "on or before", similar to what we have at question level?

Because currently it is showing me results only for "ON" a particular date. Please let me know if there is a way around, super urgent.

You can get those options if the filter is linked to a Field filter not to a normal Date Filter