My family have been granted citizenship in the U.S, we will be going for interview in three months time. What kind of questions are we to expect? Your help is urgently needed.

Don't expect much. I guess the interview would be more about collecting your documents than anything else.... not the usual as if you trying to get a visa. While you wait to travel.... acquire and sharpen as many skills as you can...especially hairbraiding . Lastly....learn to respect time...practice being punctual/on time ... be where you have to be at the appointed time without excuse....and finally... be physically fit enough to be on your feet for longggg periods.

What of resident permit and visa. Am trying to explore all avenues to avoid mistakes.

What interview are you really talking about. Citizenship interview or green card interview. Let me know which one then I might be able to help out

Sorry for the late replies, I was trying to get hold of the documents but was told that ours is still on the way. It's only my uncle who applied for us has gotten his own copy so it's kinda sketchy.
The document I saw was the first they sent to us back in 2009. It's stating immigration visa on it. So, is there any difference between immigration visa and citizenship ish?

Immigration visa entitles you to a green card. From what you are saying, you are still in Nigeria I suppose. What they just want to establish is the authenticity of whatever you have filled in the form during your processing. You are entitled to citizenship after living here for 4 years.