How to create Date fields as a dependent on Standard Fields

Summary:

1.Is it possible to only have the PO fields (PO Start and PO end) visible if ‘Payment Method’ > ‘Purchase Order’ is selected?

(Tried setting 'Depends On' Atttibute under constraints but its not working)

'Payment Method' and 'PO Number' are both Standard Fields and not custom.

2.Also,could we implement validation for the PO End date to ensure that it always comes after the PO Start date? Currently, it is possible to select a PO end date that is earlier than the PO Start date, which is illogical.