Yes, it is 7 years, and you need to be sponsored for the first five at least, then you can sort of coast on your last two years. Part of the process is to demonstrate you have paid taxes for every year so not working could raise a red flag. Once you have
PR, you only need enter HK with your card once every 36 months.
As stated above you cannot have three stars unless you renounce your existing citizenship and prove that you have done so. I think an HK passport is getting less desirable as we approach the end of the 50 years' agreement.
The process itself could not be easier. All-in about one hour of your time at Immigration Tower in Wan Chai.