Actually, I have not found this to be the case. It tends to be as much because whoever it was who "was enthusiastic" about the car is no longer so or no longer of this world.That's the reason it was parked, usually brakes and or engine has some catastrophic failure due to neglect and lack of maintenance.
Be VERY careful with the "drive".I will confirm with a drive.
And, personally, I don't. All of the fluids under discussion should be perfectly fine with the elastomer that's used for seals used with LHM. They're all in that same class of fluid and the seals should be compatible with any of them.Again - seal deterioration is the only big issue I see in the way of a substitute fluid.