If my cousin didn’t have change his lifestyle completely, he wouldn’t recover from his health problems.

If my cousin hasn’t completely changed his lifestyle, he couldn’t have recovered from his health problems.

If my cousin hasn’t completely changed his lifestyle, he wouldn’t have recovered from his health problems.

If my cousin hadn’t completely changed his lifestyle, he wouldn’t have recovered from his health problems.

If my cousin hadn’t completely changed his lifestyle, he wouldn’t recovered from his health problems.