All Unique Stunt Jumps were done by me at the very beginning of the game, immediately after the opening cut-scene where Tenpenny and Pulaski throw C.J. in the alley in Jefferson, Los Santos.
I started the game and drove around in Los Santos until I found a PCJ-600. I then rode that motorbike to the Flint Intersection and jumped over the waterway from Santa Maria Beach into Flint County. After that I proceeded to the Unique Stunt Jump.
That means that C.J. is at the bare minimum in everything.
He has virtually no Bike Skill.
He has no Body Armor.
He has no weapons, aside from his fist.
Las Ventures & San Fierro are still locked, so he has a 4-Star Wanted Level.
All Unique Stunt Jumps are done on a PCJ-600.
The Stunt Number is based on the Bradygames Guide.
NO CHEATS and no mods were used.
It's a completely legitimate game.