1. you have to install vbox additions. Select from the virtual box window -> Devices -> Install guest additions. You should have an internet connection - then an iso will be downloaded and then inside your desktop folder. Open a terminal and then
sudo sh ./VBoxLinuxAdditions.run
(see if the file name is VBoxLinuxAdditions.run or change it accordingly. Now reboot ubuntu.
2. For USB you need vbox in PUEL edition (the opensource edition does not support USB).
Uninstall the existing vbox and then install the new edition.
3. For sound, check if you have enabled audio (look in the right side of the image). Enable alsa audio driver: