Are Nigerians allowed to travel to Nigeria with expired passport s

That is absolutely not true. Do it right. Go and apply for emergency travel certificate (ETC). It's $150 money order, a print out of your ticket, a written application for ETC, 2 passport photos. Of you have accompanied minors, you do same for each and write a letter of consent dukky signed by both parents and a copy thier birth certificates. It takes 2days to process. When you get it, before you travel, make sure you make copies of the ETC, because they will collect it at the point of entry in Nigeria. Then when you are coming back, you present the copied ones. Coming back with it is only possible when you have a US passport or GC. I hope this helps.

Yes you can but be ready to give bribes to the immigration officers. Sorry to hear the truth