P.16 from the FAQ for Missions
Rating and Availability
Any gear, including magic, cyberware, and bioware, may be purch
ased at character creation, provided the Availability is 12 or less and the Rating is 6 or less (SR5, pg. 94). Note that the Damage Value and Armor Rating of
an item is not included in this, it is only items which have variable rating levels which you may be purchased. Players may purchase normal, alpha, and
used cyberware at character creation, but not beta or deltaware. Note that cyberware grade only affects the implant costs for implanted cyberdecks and commlinks. The link or deck cost remains the same regardless of whether it’s a used implant or a delta-grade implant.The only exception to Availability limits during character creation is the Restricted Gear Quality (Run Faster,pg. 149).
So, much of the discussion in this thread seems moot as Fake SINs of 5 or 6 are beyond the Availability of 12 for character creation.