Does reference collapsing happen or not when casting

Question

I am a bit confused when casting a reference to another reference. I am thinking of this in two ways and I don't know which way is correct. Here are the two ideas:

1. When casting a reference to a reference, reference collapsing happens. This means that whenever you cast a reference to another reference, it collapses to a reference(either LValue or RValue). For example, I use static_cast to cast a LValue reference to a RValue reference, it collapses down to a LValue reference due to reference collapsing rules.

2. When casting a reference to a reference, reference collapsing does not happen and just turns the reference to the other reference. This means that if I was to cast a reference to another reference, there is no collapsing rules and it just turns the reference to that specific reference(either LValue or RValue). For example, I was to use static_cast to cast a LValue reference to a RValue reference, it would become a RValue reference because it just turns the LValue reference to a RValue reference without reference collapsing.

These explanations are probably pretty hard to understand so if you have a hard time understanding them, just comment and I'll try to probably make it easier.

Here are some code snippets:

For the first one:

std::string func(std::string& LValue) {
    return static_cast<std::string&&>(LValue); // Does this cast it to an RValue and then reference collapsing happens causing it to become a LValue?
}


int main() {
    std::string t = "Testing";
    std::string& t1 = t;
    func(t1);
}

For the second one:

std::string func(std::string& LValue) {
    return static_cast<std::string&&>(LValue); //This casts it to a RValue. Does this turn it to a RValue and no reference collapsing happens resulting to a RValue?
}


int main() {
    std::string t = "Testing";
    std::string& t1 = t;
    func(t1);
}