(i) The original sentence uses "can," indicating ability or possibility. To show compulsion, the modal auxiliary "must" is used, implying obligation.
Rewritten: We must accept our life gracefully.
(ii) To begin with "No sooner," invert the subject and auxiliary verb (past perfect "had" for past tense), and replace "as" with "than" to form the correlative structure.
Rewritten: No sooner had I entered the post office than the Post Master presented me with a telegram.
(iii) A rhetorical question implies an obvious answer for effect. Transform the declarative sentence by adding "Does...not" to emphasize the mother's role.
Rewritten: Does the mother not look after her child?