I am trying to target same project file to .Net framework 4.8 and .Net 8.0.
and
Same project file to .Net standard 2.1 and .Net framework 4.8.
Please let me know whether I can achieve above two things or not.

My project is already created with .net8.0 and now am trying to target same project to .net framework 4.8 as well.
So that above project should build for both .net8.0 and .net Framework 4.8.
I tried using multitargeting in csproj file.
net8.0;net48
But while building the project ,I ended up with encountering errors.

same like this
I tried to target same project to .net framework4.8 and .net standard 2.1
netstandard2.1;net48

Please guide me whether this above 2 things are possible or not.