Anawack is the person who made it popular to let turn on their consoles with accounts in activities (or whatever) to allow the community to do certain glitches without asking a friend for help. Today, “joining Anawack” simply means joining an AFK account (whether set up by the real Anawack or not).
In fact, anyone can be used to replace an AFK account.

No, you can join the account without adding it as a friend simply by going on his profile.

There are many reasons why you may not be able to join an account:

• The account is no longer active for X or Y reason (it will be removed from the list soon if this is the case)
• The account is temporarily unavailable due to a breakdown, a console/GTA update, etc.
• A bug in the Playstation/Xbox services that temporarily prevents you from joining the account

If you are unable to join an account, you have two options:

• Wait until the account is available again
• Ask a friend to put his account in the same situation as the account you can't join

To replace an account by a friend, you must ask your friend to put his account in the same situation as the account you want to replace (situation is indicated on the cards above). If the account you want to replace is in a public session, with free aim and in the settings of an activity, your friend must do the same.