Right, so we all know Bobby would get a light sentence for murdering Lucy. I'm wondering if this is his revenge for Ian and Jane taking him out of his school? He must know they'll get heavy sentences for covering it up and lying to the police. This might be his revenge for them taking him out of his fancy school

I don't think so, I think he wants to get the guilt off his chest.

no, his revenge for being taken out of school was whacking Jane over the head - he admitted that last night

as for the Lucy admission - it just came out, I dont think he was actually thinking when he admitted to killing her at the police station or in the pub

So why did he mention the music box?

To make them believe him.

I think Bobby feels bad about what he did to his sister and just wants to get it off his chest.

because he wasnt believed - I think he feels guilty about what he has done

Aside from Stacey who's the only one to give a toss about Max, Bobby has ironically been the only decent person this week so far. While the Mitchells and Beales act like slimy scum bags, he is doing the right thing.

He's too young/naive/oblivious to know this. He thinks saying "I didn't mean it" will save him from being punished, so there's no chance that he has any idea that anyone else will be punished.

I think he's just fed up of it being dragged out like everyone else and wants to confess so that they can hurry up and end the storyline lol.