1- He said to his friend, “Let me go home now”
He asked his friend to let him go home than.
He asked his friend to let him go home right then.
2- “By God”, he said, “I do not know his name.”
He said with an oath that he did not know his name.
He swore to God that he did not know his name.
3- I will say, “Mother, I will always obey you.”
I will promise my mother that I will always obey her.
4- He said, “Good morning. Can you help me?”
He baded me a good morning and asked if I could help him
He bade me a good morning and asked if I could help him.
CORRECTION OF SENTENCES
1- Please tell me where is your brother?
Please tell me where your brother is? -YES
2- He is the most cleverest boy in the class.
He is the cleverest boy in the class. -YES
3-Your writing is inferior than him.
Your writing is inferior to his. -YES
4- I have met him last month.
I had met him last month -TRICKY
Because of 'last month', you would have to use the simple past tense:
I met him last month.
The sentence, "(I recalled that) I had met him the previous month." is OK