On modern cars which are packed with electronics, no. On much older cars up to around the mid 1960s it was not uncommon to find 6v or 12v positive earth (US=positive ground) cars, and as 12v negative earth became standard many owners converted the battery polarity. The starter motor needed to be replaced, and the dynamos which were commonly used instead of the later and far more efficient alternators could easily be converted, although many owners took advantage of the change to upgrade the charging system by replacing the dynamo with an alternator.

On the battery itself, yes... but a lot of capacity is lost permanently in the transition. Both plates are lead alloy grid and polarity is just established the first time it is charged.

Not without damaging the battery

NO.............and it's nothing to fool around with you can explode a battery so easy, and get showered with the sulphuric acid