"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."
You only have to move back in if you want to renew the six year period (maybe that's what you meant?). If you're selling, just sell within the six years and you're good.
From ATO
"To qualify for a full CGT exemption, the property must have been your main residence from when you acquired it. If you move out of the property and rent it out, you can continue to claim an exemption from CGT for up to six years after you move out. If you do not rent it out, you can claim a CGT exemption for it for an indefinite period after you move out."
