Tạm dịch: Hơn 20 năm rồi anh ấy chưa về lại quê hương.
*Ta có:
S + have/has + NOT + V3/-ed + since/for …
<=>The last time + S + V(QKĐ) + was + time + ago
<=> It is/ has been + [thời gian] + since + S + (last)+ V2/-ed
=> Đáp án: It is over 20 years since he last went back to his hometown.