Does putting a question mark behind a statement make it a question??

It makes it a rethoric question. Not a standard question.

I don't think it's that important. Most people should be able to differentiate between a question and statement with or without the ? mark.

Not necessarily. Questions in English often require an inversion of the subject and verb, for example.

Like Ellissa said, it might mean you're just wondering about something. Like hmmm 🤔

means they are looking forward to a response

Sure it does?

Meow?