Some people find letters easier and some find numbers easier. It depends on the person doing the memorizing.
I assume your talking about your driving license. Probably around age 16.
no you can not because maybe alot of people have the same last to liecenc plate numbers or letters
The different alphabets of the world, are produced by the people who use them. Numbers are produced by those same people. Numbers are also used in languages that do not have alphabets.
Need business license, tax ID#, export license, insurance etc.
yes
fmgxfgndbxvbcdgbzdczdfkjzsmfbsdfbkhgk is a series of letters that can not really be understood by a normal human. These series of numbers are often created by strange people that have nothing better to do than smack random letters/numbers into their keyboard.
ESL license is a license that allows you to go around and teach people ESL and get paid later on in life. To get information on applying for an ESL license is in certain districts.
Numbers are not needed to communicate. If you are asking about an address people would hand deliver letters to people. Towns and viilages were never so large that someone did not know them.
three letters (or County #2 if people choose to use the old (prior to 2002) numeric system)
If you are talking about the letters websites make you type in from an image, then they are called CAPCHA's. These are used so that people can not write programs to automatically login or guess passwords.
A null set. Although they could be sets of letters, sets of people, sets of animals, in fact sets of anything other than numbers.