That happened to me once. I named my tamagotchi after a second gen who had died as a teen, and was a kina as a child. I fed it many snacks, and other than that, I don't really remember what else I did. BeautifulFool's avy does rock! Where did they get it? (gaaah! Improper english! I'm assuming 'they' would be a 'she' though...)
I purposfully killed my tama on gen3, then, when it turned into an angel I brought it back to life by pressing the a & c buttons together...well...there you go...It went back to gen 1 and turned into a Kinakomotchi!