How JVM works? I am developing Similar Virtualization

My company has been assigned the task of developing a general-purpose virtual machine, similar to the JVM, to run our own custom bytecode and scripts. I understand how the JVM works internally, but I don’t understand

How a entry `.class` file is recognized as a unique application on macOS and having separate doc icon? How the class files communicates Java Runtime Environment?

PS: First I thought to develop a complete new OS like environment, means the VM considers the byte code as document & it'll have own doc, application gallery, install/uninstall system.