When Britney leaves the dance room after rehearsal of "I'm a Slave 4 U", a song that was released in 2001, there is a "No photos, no cellphones" sign. The cellphone is designed like a smartphone, which didn't exist until 2007.
During the Las Vegas scenes with Jason Alexander there is a shot of Las Vegas shown with a Poster of "The Mirage", announcing the performance of Terry Fator. Terry Fator didn't appear in "The MIrage" until 2009 while the short marriage between Britney and Jason Alexander was in 2004.