And can that wallet be hacked if I don't input any kind of malicious file or connect the device to Internet?
Chances are low if you are not connected to the internet because you're not capable of downloading an app that contains malware that might steal your info or you'll be asked to fill up a form including your private key. The usual hack that I've read is the wrong and scam websites or app that have been downloaded.
It's still a matter of how you will keep your private keys while not being connected to the internet.