UN Comtrade only stores the latest data update. In your specific case, the latest Bangladesh 2004 was uploaded on January 2007.

We are working to improve revision control so that user can find out when is the first publication, full revision, etc. However, as for now, user can only find out the latest uploaded data.

 As for Bangladesh, all data from 2000-2004 were uploaded on January 2007:

http://unstats.un.org/unsd/comtradedist/refs/getDataAvailability.aspx?lowT=2004-01-01&r=50&isOri=true&y=2000,2001,2002,2003,2004,2005

note: isOri = show only original reported classification only