Changing gear oil GY6 Trailmaster Blazer 4 150x
 

So I've seen a few videos on youtube for changing the gear oil in a GY6, but the bolts for me don't seem to line up...

I'm thinking the drain plug is this one (the one all the way to the back?)
https://photos.app.goo.gl/x986Wrtc9MyEi2mRA

But that would mean I still don't know what that middle one is...

And the fill bolt isn't where any of the videos I find show it... I'm thinking it might be this one, and you just have to be careful to measure how much oil you put in?
https://photos.app.goo.gl/GwyFs8Yh76gFvh7K9

I also have this terminal hanging off, and I have no clue where it's supposed to go:
https://photos.app.goo.gl/9EAGMZuvSM2Ec9uH9

Any ideas?

I'd need some context for the first two pics; if you could step back a little and take the same pics, that might help.
If the colour code is correct, that connector has a ground and a switched positive (meaning it's only hot when the key is on). If you have a test light, you can confirm those two wires. Was it delivered with that connector unplugged? If so, perhaps it's an optional item. If that's the case, you could change the connector, fuse it and use it for another device, like a USB charger.

This is just like my daughter UTV. The drain plug is the one with the blue mark next to it. The fill bolt is the one you have the light shining on. The oil level will be to the bottom of that fill hole. Not sure what the connector goes to.

Wow... so it has a good amount of gear oil in it, then... I can get some more pics also to be sure, but I have it tucked away in a neighbor's garage until Christmas Eve, so I'll have to wait for a good time to sneak over there and get those.

One other question... The engine doesn't seem to rev very high at all, and as a result it doesn't go past ~10mph. Is there somewhere I can adjust that, or do those motors just not rev up much? Any suggestions on getting a little more speed out of it? I know it's a heavy beast, but if it's going 10mph with just me in it, I'm worried it will crawl once I pack my kids and wife in it with me.

There will either be a adjustable speed limiter stop screw at the gas peddle or at the carb. On our UTV it was at the peddle.

Here's a video on how to adjust it. A little different than my UTV.
https://www.youtube.com/watch?v=pw_KwIFg6Vs

J-Hawk is correct about the adjustments; once you set those properly... my 150GY6 has been GPS clocked at 32mph with stock gearing. Far faster than I care to go with the wibbly wobbly stock suspension and knobby tires. Between bouncing and bump steer... woo baby yeah no. 20-25mph is more than fast enough for what I do on a utility style atv.

You guys should have fun with this one once dialed in!