Runtime features (any language)?

Question

Programming

By runtime, in this case, I mean not the environment, but the process of executing the program.
There were several questions on the theoretical part:
1) Does any language have a runtime? It's just that for scripting languages ​​it is a fraction of a second, while for other languages ​​in which demons are written it can be very long
2) Is it possible to change the program's operation at runtime?
3) If you need to replace (update) the demon, but you can’t stop the current one, then the output is only in the second server on which the updated one rises and everything switches to it?

Answer 1

1. The answer to your question is language specific. For example, Ce, as far as I know, does not carry an additional runtime overhead, while golang has its own runtime, which is associated with memory management and support for language-specific features. For scripting languages, the runtime is even more difficult, and therefore they take longer to start, even if further jit compilation is connected and the payload is executed cheerfully.
2 + 3. The overwhelming majority of the answer is no, it is impossible to replace the program loaded into memory. Erlang seems to be able to do it normally, but even there it is aerobatics.