Meh, I disagree in that I didn't hate the episode per se, it wasn't my favourite but I like it cause of the lulz and kawaii moments mainly.

About the plotholes, sometimes you have to sit back and remember that we're watching a kids show. We're even lucky that we get consistency of any sort during the other episodes.
The easiest thing to do, is remember that we're watching a show meant for kids, who don't notice such things, and just enjoy the episode for what it is, I know I did.
I mean, it's kinda impossible to hate the episode when you see something like this?
<img src="https://i.kym-cdn.com/photos/images/original/000/468/395/316.gif"

You know, the "plot holes" you pointed out can be explained easily.

1. The Code never came up before because Spike only recently came up with it, meaning it wasn't in place when he got saved by Cadence and Rainbow Dash and the like.

2. The reason Spike is being so clumsy is because he was not raised to do farmwork or cooking and therefore doesn't really have the ability to use a mop or a bucket properly. You try using a tool you've never used before and tell me how easy it is. I dare you.