Futékati et l'extraordinaire Niko Cacao

Futékati has a great passion for puzzles. Could you help him find an explanation for these mysteries: why does Célia hate him? How did Futékati inherit Niko's cocoa cup in which she had slipped some salt? Who ate the clementine that the teacher had intended for an experiment? Why is it impossible that Niko spent the whole afternoon revising his homework, as he claims?