Yes, multiple .NET Framework versions can be used on the same Windows hosting accounts at the same time. This is due to the fact that various apps might demand different versions of the .NET Framework to function correctly. IIS 8.0 on Windows Server 2012, for example, supports all .NET Framework versions supported by Windows Server 2012. This means that ASP.NET apps can run on IIS 8.0 with .NET Framework 3.5 or .NET Framework 4.5. IIS 8.0 hosts several .NET Framework versions in different application pools, allowing many ASP.NET applications with different .NET Framework versions to run on Windows Server 2012.

Almost all Windows hosting providers allow you to run multiple .NET Framework versions on the same server and give you tools and options to choose which version to use for each website or application. You may be able to specify the version of the .NET Framework in your web.config file or in your hosting control panel.

However, keep in mind that having multiple .NET Framework versions on a single server can complicate account management and might require more resources to maintain. Before attempting to run multiple .NET Framework versions, be sure your hosting provider supports it and that you are comfortable with the procedure of configuring the versions for your apps.