Cashrewards with Optus Port out Then Back in?

I'm looking at the $150 cashrewards on a new phone and plan signup for my wife but she's already a customer so I assume it won't work if she upgrades?

so I guess it will work if I port her service out and then back in? Does anyone know how long you need to port out for? was hoping just a month?

would you need to port out to another network or could she also just transfer to amaysim?

cheers