By “power switch,” do you mean what Apple calls the Side Button? If you hold the side button for ~4 seconds, does the “slide to power off” slider no longer appear? When your iPhone is unlocked, does tapping the side button no longer lock the phone?
I don’t know what “Home/Power routine” refers to, Apple says to Restart your iPhone (on an iPhone 7), hold the side button until the power off slider appears, use the slider, then once the phone is completely off, hold the side button again until the Apple logo appears. The Home button isn’t involved.
If you simultaneously tap the side button and Home button, the iPhone will take a screenshot of the phone. If you try to simultaneously press the side button and Home button, the iPhone will ignore the side button and activate Siri because the Home button was pressed (I think this has always been the case but with iOS 14, Siri just shows it’s icon instead of blanking out the whole screen).
Problems with swiping between screens or dialing numbers on the keypad sound like a separate issue, having to do with the touchscreen. If you can restart your iPhone, I’d try that to see if that problem goes away.