ya I think so
The Canadian version of the alpha black is called the "bravo one" because the US one is sponsored by the US army. So, yes, they are legal to have in Canada.
No, you can not fit a double trigger in any of the US Army tippmanns.
They are cheap, durable starter markers. compared to most walmart guns, they are great. compared to mid level markers they are not.
Price or usage?
Since the Diablo is almost a hundred dollars more, you will spend better money getting an e grip alpha black. Diablo does not have a reputation for well built markers.
The tactical edition has a 4 point butt stock and an 11 inch barrel and, M4- style barrel shroud. Otherwise it has no stock and a stock 8 inch Tippmann barrel.
The sierra one is the Canadian version of the Project salvo, which is the higher end version of the alpha black. If you want to save money for slightly better looks, get the alpha black.
It has a switch that you can choose between four settings. One is semi-automatic another is 3 round burst shot and the last one is fully-automatic.
It could be that your bolt is dirty or need to be lubed.