Nigeria is perhaps one of the largest west African countries, both population-wise and size-wise. It's ethnically and religiously very varied, which does cause some social and political problems, despite the country's reputation as a developed and especially industrialised state.
Nigeria borders Benin in the west, Niger in the north, Chad (partially) in a bit of its northeast, and Cameroon in the east and much of its southeast. Most of its southern border consists of its Atlantic coastline, geographically part of the Gulf of Guinea.
None that we know of.