(1) patrolling the river and guarding the sea: Yan's troops patrol the front line of coastal defense in Zhejiang. Guest soldier: This refers to the British invading army.
(2) Sorrow throat: low and dumb singing appearance.
Xiao is as idle as my generation: an idle generation.
(4) Qingge: It originally refers to Qingge, but actually refers to elegy.