You can, but it will take you far longer, since each time you turn something off, you then have to go back to the meter and check the readings over a few minutes.
The display for the smart meter can be carried around the house, and shows instant energy use.
It is perfectly possible to work it out with a standard meter, much much easier and quicker with a smart meter.
No, it isn't. Standard meters can only show the total amount you have used since you last read them
The smart meter shows you the exact amount you are using at any instant, and can also show you the cost of what you are using, how much you have used today, or this week, you can set a budget and it will war4n you when you are exceeding that.
It does a lot more than just record the total amount of energy you have used.
If that were true, the government would not be having to require the energy companies to fit them, setting targets for the numbers they must fit each year.
That depends to an extent on where they are, how easy they are to get at. Ours (like most in houses built in the last 30 years) are on the outside of the house, and while many are near the door, ours aren't, they are about 10 yards from the front door, all on lawn rather than hard path.