Or, more precisely: How many new major passenger planes a year that are trying to imitate the same type rating as an older aircraft do they have to test a year?

Or, more precisely: How many new major passenger planes a year that are trying to imitate the same type rating as an older aircraft do they have to test a year? In that specific case probably the important parts to review are the bits that try to make the new airframe handle the same as the old one.