No signed message? Are you the real owner of this account? You reach 850 activity and you didn't post or pm a bitcoin/altcoin address?
How many months I need to wait for this to become a Legendary status?
Activity: the Legendary membergroup has no universal activity requirement.
You are guaranteed to become Legendary somewhere between 775 and 1030 activity,
but the exact point in this range at which you become Legendary is random per user.