Yes
It can accepts anything from aphanumeric be it only 
numeric, alphabets, combination,

yes,
It should accept numerics,alphabets.

eg:If u want Name feild to accept alphanumercs.

1.Abc123def
2.123abc234def(if name field has condition like first
position should not accept,it wont work.If there no such
condition it will work)
3.abcd123

yes,
It should accept numerics,alphabets.

eg:If u want Name feild to accept alphanumercs.

1.xyzASDX123MNGFH
2.123aXZXFDDFGHbc234def(if name field has condition like 
first
position should not accept,it wont work.If there no such
condition it will work)
3.abcCSCCDRd123

yes,
It should accept numerics,alphabets.

eg:If u want Name feild to accept alphanumercs.

1.Abc123def
2.123abc234def(if the name field has condition like first
position should not accept numerics,then if u write like
this it means it has bug.If there is no such
condition it will work)
3.abcd123

If the give alphanumeri in the specification it can accept
both numbers and alphabets jointly, it cannot accept only
numbers or only alphabets.