2.( 1) Do your best: Do your best.
(2) Kneeling and surrendering: Kneeling and begging for mercy is a metaphor for surrender.
3.
(1) Never forget to serve your country;
(2) Advocating that the Northern Expedition should be recalled to China;
(3) visiting the front line many times;
(4) Never forget national unity.
The answer is not unique, just right.