The reality is any chemical may cause damage to a pony (acetone as well, go wipe a G4 with it and see how quickly it damages the pony) and each generation is made of somewhat different types of vinyl, so it’s difficult to say definitively what is or isn’t “safe” to use. My rule of thumb is to use as little chemical as possible when cleaning ponies, thus there is little worry that you are causing damage. If you feel you must use chemicals, I would at least wash the pony thoroughly with soap and water afterwards to remove as much chemical as possible, but that may not stop damage from occurring down the line.
Also, age spots and breakdown in vinyl (what the community unfortunately terms cancer) will not spread from one pony to another. It may appear to spread if given ideal conditions to develop (heat, humidity, low air circulation) but it will not transfer from one toy to another. Chemical traces can transfer however.
Elf