It depends on how you setup your Space. If you limited the amount of versions to be kept for each file within that Space then the limit is whatever you set. If you don't remember doing that then the limit is 'unlimited'. That is the default. It is also only to change the number of versions to be kept with a Professional license.
You can check how many versions are stored on the Server by clicking on the Space > looking in the "Space Information" window > and clicking on the advanced button.
Yes. I mentioned that in my earlier post. To change the amount of versions stored on the server a Professional license is necessary. It is also possible to enter a custom amount of versions to be stored on the server.