Chris Brown appeared on Saturday Night Live as a musical guest on February 12, 2011 where he performed "Yeah 3x" and "No BS." The best resource for future hosts and musical guests is the Official Saturday Night Live website, which will show you the host and musical guest on the front page.

April 1, 2011 was a Friday night. Saturday Night Live comes on Saturday nights. On Saturday, April 2, 2011, Elton John was the host, and Elton John and Leon Russell were the musical guests.

The musical guest on Saturday Night Live August 11 was 'Beck'.

Usually, the August episodes are repeats. Since this answer changes from week to week, the best resource is the Official Saturday Night Live website, which will show you the host and musical guest on the front page.