If you are a developer enrolled in the Apple Developer Program, you can download iOS 14 beta, macOS Big Sur beta and Xcode 12 beta from the Apple Developer Portal.
Now open official Apple App store by opening safari browser by signing into the App store Apple ID and password. To install xcode for windows 8.1 download, the next you have to do is follow the on-screen steps of OSX boot as Wizard and then OSX will be installed in Oracle Virtual easily.