There are actually blocks that have no transactions included. I think the payout then will be only 25 btc as there are no miners fees given to the miner
Do you have examples of these? I cant imagine why there would be no transactions unless they were very early blocks.
Yeah, these things happen. It happens if blocks are found like 1 second after each other.
Btw OP, why do you have to ask that question? Every senior member is supposed to know this.