Well, I had no other choice in the matter. I didn't have Newboy's Talisman with me in Act I and the quest wasn't active. I restarted and finished the Prologue yesterday evening and now I have the Talisman in my inventory and the quest is listed as active

Didn't have it. Must have chosen the wrong dialog options in the prologue.

Restarted the game, had to do it anyhow after installing the extended edition

Regarding Meliteles Heart

I finished the Troll Quest. When I first entered Lobinden, Geralt said his Medaillon was vibrating but I didn't think anything of it at that time. Later I looked into the game guide what side quests I might have missed and saw the Meliteles Heart Quest. Then I checked my questlog and the quest was already marked finished in the Prologue. (I told the soldier who had it for protection to wear armour, so that he survived and he helped me esacpe the castle at the end of the prologue)