alphabet :A character set that includes letters.(from Merriam Webster Dictionary)
alphanumeric binary :actually,it's a kind of patent used in a nine key alphanumeric binary keyboard combined with a three key binary control keyboard.A first set of nine binary keys numbered one "1" through nine "9",used as an alphanumeric binary keyboard,with twenty-six characters and a space grouped in sets of three's on all nine keys,combined with a second set of three binary control keys including,a first binary control key,a second binary control key and a third binary control key.
If you're dizzy about the descriptions above,let me show you a live example,most cell phones are using this nine key alphanumeric binary keyboard combined with a three key binary control keyboard.
character numeric:To be honest,I can't find any references on this phrase.Personally speaking,I think the phrase you're talking about is "numeric character",it means the coding language used in computer,say,html numeric character.
alphnumeric :Of or pertaining to alphanumeric characters(from Merriam Webster Dict).
To be frank,I haven't seen any differences between these words or phrases,for they do mean things irrelevent to each other.