My pc has been fixed: resetting to the building settings has made it work again and properly. Wi-Fi and the mobile broadband (Internet through the USB key) work perfectly fine and with Google Chrome I can visit all the websites with no issues. Movie Studio Platinum 12.0 has been successfully reinstalled with no serial key and it's working. The only side effect is... I need to reinstall all Win 8 (to switch to Win 8.1) and my AMD graphic card updates in order to play specific videogames. XD In the meanwhile, I've just finished playing Prince of Persia from 2008, a game I lastly played in 2014, and I have few other games to complete yet. XD Before I install The Evil Within and Shadow of Mordor. C: Or I can install them anyway.
As for GaFM 19, I have to redo the video completely from the beginning: its file has been lost with the resetting of the PC. No problem. Also, I won't play WHF and continue my video series for a while due to the updates problem.
It's all a question of patience to get back to where I left.