Why a machine with .NET 4 installed on it cannot run an exe that targeted .NET 4.5 while if they use the same CLR version?

Question

In Common Language Runtime (CLR) Microsoft page, it says that both .Net Framework 4 and 4.5 uses the CLR version 4.

However in this page (.NET Framework Versions and

Answer 1

By Microsoft,

Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the assembly relate to each other. The assembly manifest contains this assembly metadata. Assembly Manifest. This manifest has information about the build CLR of that executable and while executing the exe/dll .net CLR tries to find out the same CLR version. See the image, Build by v 3.5 and Build by 4.0.