Playstation store questions (also questions about test funds?)?

i have multiple questions about the playstation store on a ps3, one i would like to know if icould get money back for previous purchases, some games i do not like anymore, so i would like to trade them for (even half of the money would be fine) some sort of refund, is it possible? i would also like to know of this 'test funds' thing. i saw a video on youtube, you email psn and have <100> or something in a paragraph and you get 100 in cash! seems nice. but i think it changes every year and the vid is 2009, and the people said it worked. so i was curious if i could receive a 2011 version? thank you. more or less im trying to get the 2 new mortal kombat add ons, and trade in deadliest warrior and an addon. seems fair, yes? thank you for those who read or answered this question.