By safely i mean that it will not break the Piezo or the circuit itself
Generally, yes. A Piezo transducer has electrical characteristics of a small capacitor, so it generally has higher impedance than a speaker (at audio frequencies) which means it consumes less current/power than a speaker.
If you want to be extra-safe, put a 10 Ohm resistor in series with the Piezo.
Yes, if you use it e.g. as a tweeter, connected to an audio amp.
If you connect it to a digital output pin, no.
A 3-30nf piezo is a short for the digital switch pulses.
Better use a 220ohm series resistor.
Leo..
The other concern is that it is a resonant device and can if it resonates, generate voltages outside the acceptable range of the Arduino - probably less of a concern if the pin is only ever in output mode and the 220 ohm resistor in series.