A function is easy to call if it is a member of a class:

package com.example

class MyClass {
    fun myFunction() : String {
        return "result"
    }
}

val myClass = Class.forName("com.example::MyClass").kotlin
val myFunction = myClass.functions.firstOrNull { it.name == "myFunction" }
val result = myFunction?.call()

But what if the function is without a class?

package com.example

fun myFunction() : String {
    return "result"
}

Condition: file name unknown.
In JVM there will still be a class, it is the file name with the Kt suffix.