Because Super Angelo has been discontinued, you can't order the game anymore. However, Charlie the Duck (Charlie I, not Charlie II) uses the same registration system, so if you buy a code for Charlie the Duck, you can also use it for Super Angelo. See the website of Wiering Software for more information: http://www.wieringsoftware.nl/.
Using the following cheat you can get through the hard castle levels (requires version 2.2 or above). Press [P] (pause) and then [Tab], then type 14159 (in the first castle), 26535 (second) or 89793 (third).
Description by Wiering Software