I am in US and working in H1B Visa and wife has h4 Visa she came to USA on Oct and went back to India on Nov, Now she is not in USA, Can I file tax as married jointly?

1. Yes, if you are a US resident for tax purposes, you can file jointly with her.  You would need to make an election to claim her from a nonresident to a resident.  For instructions, click here Nonresident to resident

2. Yes, filing jointly usually gives you a bigger refund. To see the comparisons between filing jointly and separately, click here: MFJ vs MFS 

3. If you both file jointly as residents, you are required to report her worldwide income including those from India.  If she pays taxes to both the US and India on the same amount of income, you may claim a foreign tax credit on your US taxes.  For details, click here Foreign Tax Credit.

4. The filing requirements of a foreign country are out of scope for advice.  You would need to consult their tax authority for further clarification. 

Yes, you can file jointly if you yourself are a resident for tax purposes.  See Nonresident to resident
For this point nowhere mentioned the duration of stay to file jointly, Could you please help me if my wife did not stay in USA on h4 Visa more than 30 days, Still I can file as jointly and will get benefit?

Yes, you can still file jointly by making an election to treat her from a nonresident to a resident.  See attached link above.

3- I will show all her income whatever she earned in India. Can I exclude whatever she is paying tax in India?
 After declaring her India I have to pay tax in USA also is that correct?

You can claim a foreign tax credit on the amount you pay taxes to both the US and India.  It is not an exclusion that you would exclude from your income.  Instead, it is a credit that can reduce your taxes dollar by dollar.