what is the difference between an arduino duemilanove and an arduino uno (or arduino zero or sparkfun redboard)? I know that the arduino duemilanove is no longer sold, but what model that is currently sold is the most similar to it (and does all the same functions)?
The main difference between a duemilanove and a UNO is the serial converter. Otherwise..they have the same microcontroller (the Atmega 328p, unless you have a duemilanove with a 168), same IOs, same... everything.
If you worked with a duemilanove you can change to UNO and you just have to update the drivers. Old programs will work on the new one without any edit