buzztone on "[Plugin: Contact Form 7] hiding/showing fields per requirements"

Looks like you are looking for Conditional Logic which is not available in the Contact Form 7 plugin.

This sort of conditional logic is not available directly in Contact Form 7. It can be done via custom programing but you would need to be rather skilled at WordPress development using PHP.

Some of the premium Form plugins do offer Conditional Logic including Gravity Forms, Quform and Ninja Forms.