Are there any loopholes for returning a car to the dealer?

In some places there is a Law allowing a 24 or 72 hour "Cooling Off period" where a NEW car could be returned.

But not where I live.

In many US states there is a lemon law where a vehical can be returned for full refund if the Manufacturer is unable to repair a real demonstrable problem. There are rules though. They are allowed a certain number of attempts and a certain amount of time.