It's not that people dislike C/C++ because it's a bad language, it's just that it's not the easiest language to start with. There's many little things about them that you'll have issues with quickly if you don't understand other aspects of development in general. I think the biggest things are...
Yes. Yes they did.
Hey Envd. Welcome to 7S. Glad to have you man. It seems as though you're misnaming everything. I would not consider this a "simple login" but a key validation. As I assume you're learning as you go...here's a few tips.
Do not store any license keys client side. I can not...
What Cakes said is honestly easiest and smarter, it makes it so that you don't have to rewrite the same code over and over again. Tempted to do this myself actually, just because why not?
That's such an irrelevant question, you're assuming it will have the same mechanics as CoD with guns. You don't even know if the final product will have snipers...