Can instrumentation amplifier amplify a very low DC voltage?
For example, if input is 10mV, instrumentation amplifier gain is 100, is the output 1V DC voltage?
Yes, that is exactly what they do. Or, the signal is 10uV and the gain is 10,000 and you still only have 100mV depending on what you are doing, of course.
The real point is not so much the gain as very good common mode signal rejection.
I hope you don't think about creating higher energy out of lower energy, as the name “amplifier” may suggest ..
Just keep in mind one thing: amplifier needs a power supply and only then it can amplify input signal and produce desired output ..