Thanks for any help on reported speech. Both answers 1a, 2a and 3a have the tenses changed which seem correct than ans 1b, 2b and 3b.
Qn1: "Did Mr Smith question you about the missing file last week?" David asked.
Ans1a: David asked me if Mr Smith had questioned me about the missing file the week before.
Ans1b: David asked me if Mr Smith questioned me about the missing file the week before.
Qn2: "The cake that your mother made yesterday was delicious," Damien told his friend.
Ans2a: Damien told his friend that the cake that his mother had made the day before had been delicious.
Ans2b: Damien told his friend that the cake that his mother made the day before was delicious.
Qn3: "I am going home now," Candice said.
Ans3a: Candice said that she was going home then.
Ans3b: Candice said that she is going home then.
Generally we move the tense back unless the statement is always true or is still in the future at the timeof reporting. In these examples, the a) version is better because the actions are past by the time of reporting.