Hi There 
My name is Marcin and i m new user from Poland .
I have a question, Is there any chance to upgrade beta2 version of ubuntu mate to final relases? And how to do it?
Cheers from Poland
It will upgrade itself to the final release thru the update manager. No need to do anything.
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However, if for some reason the Software Updater doesn't prompt to upgrade a day or two after its release (15.10 is released Thu 22 Oct), there is a manual command that you can type in the terminal:
sudo apt-get dist-upgrade
Some further information here, including a screenshot: