In indirect speech, is it correct to write

Question

Joe asked Nelson when did Gabriel reach home or when Gabriel had reached home. Please explain

Answer 1

Yes, and here's how to see this:

Direct question (or direct address):
Joe asked, "Nelson, when did Gabriel reach home?" (past, past)

Indirect question:
Joe asked Nelson when Gabriel had reached home. (past, past perfect)

http://www.englishtenses.com/reported_speech

Indirect questions: http://grammar.ccc.commnet.edu/grammar/marks/question.htm#indirect

Indirect speech: http://staff.washington.edu/marynell/grammar/reprtdsp.html
The charts here are helpful.

Answer 2

Thank you so much teacher