He live and work in chad where he got his passport and he born and rise in Sudan where he is claiming the dv lottery
What the document he need to provide on his enterview from both countries
AFAICT there is an embassy in N'Djamena, Chad (https://td.usembassy.gov/visas/). However, as stated in a link that I provided, immigrant visas for people from Chad are taken care of by US embassy in Yaounde, Cameroon.The country he live doesn't have embassy
His obligations towards Cameroon authorities do not matter in DV process. He should check Cameroonian regulation regarding citizens of Chad/Sudan.So do he need to got visa to Cameroon in his Chadian or Sudanese passport
The country he live doesn't have embassy