Yes, not driver need for OS as it will detected as removable drive. However, it will be smart to have some kind of software to mange and sync music because ID3 tag reading isn't perfect on X3. A good music managing software will put all the music in the correctly named folder and makes browsing much easier. I use Media Monkey personally.
Yes, you can add / delete songs to the Favourite list. No, I don't know how many songs it can hold.
will add the delete feature when the mass production is released in June.