Existing idea and definition of a concept

Hello Rabbi Michi, I listened to lesson number 5 in conceptual analysis and I have two questions:
1. What makes a definition from the world of ideas exist? As you said, not everything exists, otherwise any collection of characteristics (even unrelated ones) would be defined as a concept. A possible criterion is whether it has meaning? If so, what determines what has meaning or not? So is it the fact that it can be realized in the real world? Then there would really be a concept of democracy for the beach? Ostensibly, I see no reason for it to be considered a concept, but it does exist to a certain extent in reality. You did not define what the criterion is or perhaps I did not understand.
2. Finally, you briefly described your view that the definition of a concept can be debated. The concept exists in reality and its definition can change (similar to a person growing up).
I was not convinced. It seems to me, as the American you mentioned who lectured at Ben-Gurion said, that the moment a definition or set of characteristics is changed, it is already a different definition. We use definitions with the same name for our needs and argue about them, when in reality they are really completely different concepts. We do this because it has practical implications and is a form of reference and speech, but in practice it is indeed a different concept. For example, you used the example of a debate about what a Jew is. The debate is not really about what a Jew is, but rather there are different definitions, and for the sake of argument we can call them Jewish-Halakhic and Jewish-Israeli. It seems to me that the debate will not be about what the correct definition of the concept of Jew is. The name is just semantics and the debate is about practical implications – which definition of Jew we want to use in practice, Israeli or Jewish. The winning definition will only be in our practice and we will call the winner a Jew, and in the world of ideas both definitions will remain. If we talk about a change, there was not really a change in the definition. It is possible that in practice it was decided for one reason or another for certain needs to use a different definition. The fact that the new and old definitions were given the same name is technical and semantic. In practice, this is a completely different idea and the concept has not changed, only the practice. Sometimes we change a definition because we realize that we defined a concept incorrectly. In such a case, we have not really changed a concept, but rather chosen a different concept and called it by the name we used in the past. Both concepts exist or perhaps the first one turned out in retrospect not to exist. But the choice to use the same name is a practical one that reveals our current intention and its adaptation to practical needs. It does not change an existing and defined concept. I hope I have been able to clarify my intention.