Can .NET framework 2.0 assemblies run under .Net framework 1.1?

Short answer: NO.

Long answer: In .Net framework 2.0 many features are added. Many features(Generics first comes to mind) warrant a medata format change. As a result, .Net framework 1.0 and 1.1 will not recognize assemblies compiled with .Net framework 2.0 compilers.