Login to tty as guest?

No, you can't and I will try to explain you why. There are two things that prevents you to login to tty as guest:

1. The default shell for guest accounts is set to /bin/false. You can check this with the following command (the shell is set on the last field on each line):

   grep guest /etc/passwd
   

   /bin/false is just a binary that immediately exits, returning false, when its called, so when someone who has false as shell logs in, they're immediately logged out when false exits.

2. The password for any guest account is disabled by default and this is absolutely normally: if you invite someone in your house, you don't give him your house keys.

   Because of this nobody can't login normally^[1] in any interactive login^[2] shell. You can check this with the following command (the password is set on the second field on each line):

   grep guest /etc/shadow
   

[1] I said normally, because you can switch from a real user to a user with the password disabled using sudo su user_with_no_passwd (like in real life: when someone knocks on your door, you open him with your keys).

[2] tty1-6 wast (and I suppose it will be) all the time an interactive login shell. And this world - login - it suggest me that I must to have a password to get over it (like in real life: when you see a lock, you need a key to open it).

Now, if you still want to login to tty as guest, follow the instructions from the below ttyrecord image:

And now you can go in tty and login as guest... a guest with password... which means that it is not anymore a guest...