1.

I reckon the best way to store nicknames in games are by INI files or hash tables. Vars can get very messy.

Code:
On *:Text:!Start:?: {
  if (!$readini(Game.ini,Users,$nick)) {
    writeini Game.ini Users $nick
    msg $nick You're Journey Is About To Begin, But Before That Lets Get You Registered.
    msg $nick You need to choose your character. To see the list of characters type !chrs and to choose one type !chr <Name> 
  }
  else { msg $nick You have already registered. }
}


2.

Creat a file called commands.txt in your mIRC folder and play the file to them

Code:
On *:Text:!Commands:#: {
   play -n $nick commands.txt 1000
}

-Andy