A:
I'll answer your questions in order.
1. Unless you are connecting a keyboard or a flashdrive, connecting a USB device to the Tab will not offer the same functionality as if you were connecting it to your PC. The Tab runs off of Android, which will offer different functionality for USB connected devices, and will not necessarily recognize an MP3 player as an MP3 player.
2. Again, since this Tab runs off of Android, you will need to use the actual App for the service you want to use (which will be available through the Google Play Store). This will be the case for all Android devices, and not just the Tab or Tab 2.
-MrSamsung