You have to ask your airline that, because it depends on the airlines policies.
evergreen airlines can only carry 15% of passenger
No currently Delta Airlines does not charge for carry-on luggage.
23 kg (50 lbs) and 7 kg for carry on lg
Flight schedules for most Nigerian airlines change on a regular basis so it would be a good idea to use a web site that offers Nigerian flight schedules. I would suggest Text2Fly who you can find at http://text2fly.com.ng.Text2Fly carry the flight schedules of Nigerian airlines like Aero Contractors, Arik Air, Virgin Nigeria (recently renamed to Nigerian Eagle), Bellview, Chanchangi and possibly others.
The restrictions for carry ons for united airlines states that a traveler can bring on board 1 carry-on bag because of limit in space.
NO
Currently, American Airlines allows for one carry on item to be brought aboard a flight, as well as a small personal item. The carry on has to be smaller than 45 inches (length, height and width) and fit in one of the sizer near the boarding gates.
You can have one carry on. You now have to pay at least $15.00 per bag at most airlines. There is also a weight requirement. Not sure what is the limit.
in your hands
No you do not.
It would depend on the Airlines... most of my flights (on different airlines) I carry 2 Rims of cigarettes (per person).