If bb10-0015 refers to a specific hacked firmware build you have found on legacy forums, it is likely a —a modified iOS IPSW containing Pangu's untether payload, perhaps designed for specific iPhone 4 hardware configurations that were notoriously difficult to jailbreak or downgrade in 2014.
Settings → About → OS Version. Look for non-standard numbers (e.g., 10.3.2.PANGU.0015 ).
How to Install BlackBerry Firmware BB10-0015 using Pangu