A deployed environment in Elastic Beanstalk will always be deployed with a certain application version. We are able to manage application versions straight out of the management environment by providing different packages or different S3 paths to the packages that exist in our environment. When deploying an environment in an application that has existing application versions, the deployment dialogue changes and the application code will get an Existing version selection available. Here, we can select any existing versions to deploy to the environment, as shown in the following screenshot: 

Being able to maintain several versions of the code in these environments is crucial as development usually has several stages that the code passes through. For example, we can easily maintain a development environment as well as a test, staging, and production environment, all running independently with different versions of code, as demonstrated in the following screenshot: