Question about “modal verbs in indirect speech”. Thank native English speakers very much in advance. 1. I told him he need not come if he didn't want to. 2. I told him he need come if he wanted to. 3. He said he needn't go. 4. He said he need go. 5. He felt he ought to help her. 6. She told him he ought not to do it. 7. He said the children dare not go out and play. 8. He said the children did not dare go out and play. 9. He said he should return, and he did return. 10. Mary said that I might borrow her car. 11. I said I could see you at eight. 12. He stated he used to live on the Yorkshire moors. 13. He said he would rather stay at home than join us. 14. He said that children must obey their presents. 15a. He said we must go. 15b. He said we had to go. 16a. His mother said he was not to go out without coat. 16b. His mother said he must not go out without coat. Question: Which is/are grammatically correct? Is the 15a equal to the 15b? And 16a = 16b?