BlueStacks Inc. is slowly deprecating support for version 4. They are removing old download links. If you want the offline installer, download and archive it now . In two years, it will become abandonware—and for power users, that is the highest form of flattery.
A: Yes. BlueStacks has always been free. The offline installer is simply a full package version.
Go to Settings > Engine and allocate at least 4 cores and 4GB of RAM if your PC allows it.