What will happen if I supply greater than 1.1V to analogue inputs if analogReference set to INTERNAL? I am reading a 50Hz AC voltage using the analogue inputs.

If I set the analogReference() to INTERNAL, meaning 1.1V on the Arduino Uno, what will happen if a voltage greater than 1.1V is supplied to the pin? Will the board be damaged? If not, what value will the ADC give?
You will read 1023.

The limit of the voltage is not the reference voltage but the chip supply voltage - so 5v on a 5v board.