Ironhand

The switch isn’t animated but the commands do work.

At the time the tutorial was created, the Mercury pod was being modeled (incorrectly) as being infrared, hence the tutorial description of what to look for. The pod is now being modeled more correctly as a low tech light amplification pod. So things no longer show up in high contrast as they once did. The target is on the runway centerline just above the white runway markers. The tutorial needs to be remade.
in your second set of screens, your seeing what you should see with the pod amplifying daylight—a bright, washed out screen.

I wasn’t when I tried the mission. It only works on MT?
EDIT: Problem solved. It evidently only works properly with the MT exe.

It is definitely the side slew that caused the lock issue. Centered, there is no problem. Slewed right or left, there is no ability to lock as BlackPixxel stated.

Start DCS. On the main menu at the top is a box with numerous squares. That’s the module manager. Click it and hopefully you’ll see the F-15 there ready for installation.

Yes, you can. I do it frequently to change the time of day, cloud cover, add eye candy, or extra units.
While in the ME, use the Open File button. Change the file type to TRK. Locate and load the track file into the ME. Make your changes. Save the file. When saving, make sure that you have the type set to TRK. Otherwise it’ll be saved as a mission file.

You can do it with TrackIR.
To address your example, though, the easiest way to do it  would be to set up an AI vehicle to overtake the “target” vehicle and use it as your view platform.

Only if you use the old clouds. Select NONE for the presets and, then, use the sliders to set the cloud base and thickness for the old (very old) clouds. Finally, select "10" for the density.

It's a matter of Gs. You can't pull high Gs long enough in the Su-25T to blackout. You'll break the airframe first. This was one of my more spectacular attempts:
 
Take a look at the -25T's G meter. The "danger zone" starts at 6.5 Gs. If you stop there, it'll take a long time for much of any "blackout" to happen, if ever. If you push past bad things happen too quickly. The attached TRK file isn't the YT flight but you'll see what I mean.

 
Here's the MiG-29's G meter for comparison. You can go all the way up to 9 Gs before you hit the red zone:

 
Su-25T G Effects.trk