Determine which .NET Core runtime is needed

I found some interesting articles about the difficulties of .NET Core SDK/runtime/tooling versioning, for example:

• .NET Core Versioning
• .NET Core versioning
• Supporting both LTS and Current releases for ASP.NET Core

However I still don't really know how to deal with all of this in practice:

1. Given a project with a number of .Net Core dependencies. How can I determine which version of the runtime needs to be available on the end-users machine?
2. Does the runtime version need to match exactly, or can the runtime installed on the end-users machine be newer than the required version?
3. Let's say I want to stick to some LTS version of the runtime. How can I determine the version of the packages I need to reference? How can I make sure that no newer packages are referenced?

Oh, and there is one more:

4. Once I know which runtime version is required on the end-users machine, how can I determine (programmatically) if that version of the runtime (or a newer, backwards compatible one) is available?