LM35 has about 1 DegC accuracy around 100DegC. Interchangeability refers to when you take another unit and replace the first unit, what it the different in reading. Say sensor 1 says 100 and sensor 2 says 98.
Arduino's 5V reference is probably around 5.05V. You need a good voltmeter (3.5 digits or 4.5 digits) to get an accurate reading of the voltage. If you have a 2.5 digit meter (shows 3 digits but leading digit is only 0 or 1), you won't get an accurate reading of the arduino 5V.