Complex sentence: Some of the Terai lands were gifted to Nepal in 1816 and more were gifted in 1860 as thanks for helping the British to suppress the Indian rebellion of 1857.
Split into simpler sentences: Some of the Terai lands were restored to Nepal in 1816. More Terai lands were restored to Nepal in 1860 to thank Nepal for helping the British to suppress the Indian rebellion of 1857.