Two questions, please:
1) If I have an account in a Nigerian bank, am I able to make fixed deposit from my Savings account while in diaspora, or by money transfer from abroad for fixed deposit?
2) Is it possible to open a bank account in Nigeria without physicality being in the country? If yes, kindly provide a list of Nigeran banks that allows it.
As for your first question, the bank in question that you would like to make a fixed deposit should be able to answer that.
As for the second question, it is practically impossible as your passport and details including your bio data and signature would need to be taken in order to open an account in Nigeria.