4 points
Yes, there’s a queue called mempool.
Clogging up the network is possible, but costs money (BTC), because transaction fees need to be added to the transactions and those fees need to be higher than those of the highest not yet processed transactions if “regular” users’ transactions shall be delayed.
Miners prefer transactions with higher fees (to be precise: higher fees per occupied block space), because they earn them when creating the block successfully - together with the BTC that get issued when a block gets created.