about the invitation letter from Duly Authorized Unit

1. Does the invitation need to go through China authorized Chinese unit?

2. What is the name of the authorised unit?

3. The original invitation letter sent to me from a company in China with all verification (stamped and signed) is it not valid to the China Embassy in Nigeria?

4. How many working days will it take the China Embassy in Nigeria to issue one the M Business China Visa after meeting all the necessary requirements needed?

5. Please is there any special way the company inviting me should address the letter i should take to the China Embassy?

6. Will the China Embassy in Nigeria accept the Invitation Letter sent to me by this company Guangdong Forstar
Precision Machine Co.,.Ltd from China for a 2 weeks Agency Training in China. duly stamped and signed.
Best regards,
Obayagbona Caspar Pedro.