I find it ironic that you say it's for GD, yet this work can't be used xD
Anyhow, My take on it:
You had the melody down, some tweaking and it would've sounded like the real thing.
At :30 The chords sound... off. I don't know if it's echo or what, but that could've done without.
Other than that, everything else is pretty spot-on for me. 4/5 for you sir!
GD Level coming soon! I guess...