Does Unity Automatically Runs Garbage Collector, or Have a Similar Stuff That Automatically Runs?

If not, is it a good idea to make a regular invoking method for garbage collector?
Thanks.

Yes it does, you can read more about it in the Documentation on Understanding Automatic Memory Management

Yes.

Unity runs garbage collection duties; it’s not something you need to manage yourself. However, it is still a performance consideration in most cases. So having an awareness of it is definitely a good thing.