Answer
Yes. Plesk supports both these .NET versions as in fact 3 and 3.5 versions are .NET 2 with additional set of libraries. And Plesk supports .NET 2 since 7.5.6 version.So to configure domain to use these Framework versions it is necessary to enable ASP.NET 2 support on Setup page (Plesk, Domains, domain.tld, Setup) in Plesk.