Unfortunately, the ADC that reads analog voltages cannot handle voltages over 2.0V at all (though I recently learned the ADC has some protection circuits that should prevent from actually breaking when you connect a higher voltage, which is good).
The biggest internal AREF available is 1.8V, so you can only meaningfully read values <= 1.8V. If you really need it, you could connect an external reference voltage, but only up to 2.0V.
Does this answer your questions?
On a related note, I recently thought of a way to "abuse" differential analog reading to double the effective analog range (to 3.6V). In differential measurement, voltages can go from -AREF to +AREF, so if you subtract your input signal from 1.8V/AREF, you double the range. This requires shorting AREF to a second analog pin and needs support in the code. It might also not work at all - I haven't tried this yet.