you can only have one PPR at any point in time. If you want to alternate properties the ATO may question the reason why you would continue to swap properties. If they decided that you were doing to avoid cgt you would get caught under Part 4A of the tax act.
If you live in your home from day one and wish to move out you can do so for up to 6 years however you must move back within that 6 year period provided you have no other home you are wanting to claim as your PPR.
If you genuinely need to move in and out of your 2 properties then you must keep a timeline of the 2 properties. Both properties would be subject to CGT for the number of days it was no longer your unless both properties are pre Sept 85
