Grudge, as far as I know (I may be wrong) we can not register a name that is of length 2 characters or less
From - *www.registry.in/policies/
# Domain length: .IN domain names may be between 3 and 63 characters in length.
I also checked my friends site who offer .in domain. It also says the rule
# Domain name too long/short This means that the domain name that you entered was either too long or too short, legal domain name lengths are between 2 characters and 57 characters.
# Domain name cannot contain any letters of hyphens in 2 character domain names This error message is returned if your domain name was only 2 characters long and it contained either a hyphen or a letter, this is because 2 character domain names are only allowed to contain numbers.
This is for .in domains. Not sure about other
This is not the final word, please check with some one expert in this area.