You can log PIC time any time you are the sole manipulator of the controls of an aircraft for which you are appropriately rated. It doesn't really get into any more detail than that. So:
You can log PIC in all of the examples above.
You are not acting as PIC during an IFR flight with an instructor, as the instructor is the instrument rated pilot. Also, if you are wanting to be an airline pilot, chances are time such as this wouldn't be considered as part of your PIC time for the sake of the airline's needs. In fact, I remember only adding up time that was PIC and NOT dual received to get my PIC number for airline applications.
During simulated instrument, it could be argued that you are still acting as PIC, with the instructor providing safety pilot services (as well as instruction, but that's not terribly relevant for the logging discussion.)
I'll leave the sim question for someone else, as I have an idea, but don't know for sure.
Corrections would be best made via a single line, an initial, and possibly even a note below indicating why it was deleted. Official type people don't like white-out.