Do you think being sedentary is literally not moving at all throughout your day? Doctors generally recommend at least 4-5 hours of vigorous exercise a week, getting up and circling your apartment a few times each day is not equivalent.
No, I go and do an exercise regime every hour, why would you just walk around your home? Waste of time to not exercise hard.
Moving a few minutes regularly throughout the day? You just described being sedentary.
Nah, if you max out your pulse 30 minutes a day you aren't sedentary, and that is just 5 minutes 6 times a day. It is healthier to spread it out like that rather than sit still and do it all at once.