I was playing around with the debug window and once I thought that I saw that I was connected only to one peer, so I was also wondering if there was a minimum number of peers parameter somewhere in the qt wallet (so that for example if you don't have enough peers, you can't maker any payments?).

I am sure there could be examples where you pay for something and then wait for confirmation for a day and meanwhile change your mind.
You could also make another transaction (with different coins), but then the bad peer let's the previous one trough and you spend twice the amount, anyway it was a theoretical example, so that I can plan a better attack khm... understand the network in a better way  .

Hello.

I was wondering if a delayed payment broadcasting attack was possible?
I mean: if A wants to pay something to B and sends the payment confirmation to a peer C, then C can postpone the broadcast of the payment to the rest of the network. In this case A sees that the transaction is unconfirmed and thinks that the payment didn't get trough. If A then decides not to pay B with another broadcast of the payment, C can still make the broadcast of the transaction at any time.
So theoretically if A will not spend this coins, C can make the broadcast a year later?

If this is true, then if you have an unconfirmed transaction and you changed your mind and don't want to spend the coins, the best solution is to create another wallet and resend the coins to your second wallet?