No, look at the real life constraints of the problem. The screensaver can be prevented from starting by using SetThreadExecutionState or moving the mouse. Another app can't stop you from making the system unidle.
And in the second part you're not paying attention to the constraints. If you want to simply kill all programs, that's easy in windows. The problem described above is to keep the system running, but become the topmost window. So a solution that causes crashes is not a solution.
Crashing a windows program is trivially easy, and it would "solve" the problem, but that's not the right kind of solution.
You could restart them all again after your program is done. Of course, if the other programs do more than just display a message, which is hopefully on disk rather than just in RAM, then you'd still have data loss, so... yeah.
And in the second part you're not paying attention to the constraints. If you want to simply kill all programs, that's easy in windows. The problem described above is to keep the system running, but become the topmost window. So a solution that causes crashes is not a solution.
Crashing a windows program is trivially easy, and it would "solve" the problem, but that's not the right kind of solution.