I am speaking Spanish with someone on Skype and I KNOW it is improving my Spanish. "I hear and I forget. I see and I remember. I do and I understand" is attributed to Confucius. Learning by doing is an important part of the process. I always have "mike fright" before talking to someone in another language. It is always challenging. Teachers make everything easy because they speak slowly and carefully and use simple vocabulary and grammar. "The real thing" is much harder.

Yes, a lot.. communicating is also best for learning ☺

As long as they correct your pronunciation and your grammar. Otherwise, I think it is not useful.

I do not see why it would not help... So yes!

Yes , for sure