Block incoming calls from specific numbers during specific time frame

I think your best line of action here would be to send Feedback to Apple for a feature request. As you know, Do Not Disturb can be set to allow phone calls from selected people during specific time periods, they could also include an option to not allow calls from specific numbers during a time period.

As for app recommendations, developers do not have access to the phone number when a call is received, so there would be no app that would be available that could do what you describe. There could possibly be a service similar to a robocall blocker that intercepts calls before they arrive on your phone, but I am not aware of any that let you specify calls to block during a specific time frame.

Product Feedback - Apple

You can do that with focus.

It's not a separate app. It's built into iOS 16.

Settings>Focus.

You can modify an existing focus mode or create a new one with the settings you want. You can set a schedule to activate a specific focus mode or enable it based on location.