The vinegar/acid test only works to determine if the rock is or is not calcareous. Calcareous means composed (made) of a calcium type mineral such as limestone, dolomite, marble, lavarock. The "fizzing" if it occurs means some such mineral is in the rock, and this will dissolve slowly into the water, raising hardness and corresponding pH. So this test tells you nothing else about the rock. This calcareous rock is fine in livebearer tanks or rift lake cichlids, but should not be used in tanks with soft water fish.
Rock is porous depending upon the type, and thus absorbs liquids. If it was exposed to oil, gasoline, fertilizers, pesticides, etc., these may be in the rock. I am not sure that any amount of washing can remove these substances. And along the same lines, I would not recommend using bleach to clean rock, as this will also be absorbed. Same with salt water. The amount released over time may be minimal, but still doesn't belong inside a fish tank.
A good scrub with a stiff brush under hot water is all I use on rock. I have used lace rock purchased from a fish store, and I have used basalt slab rock and rounded river rock from a landscape supply. I recognize there is a risk to any rock (or wood for that matter). "Soft" rock that crumbles should never be used, only rock that is hard.