If I lose Wi-Fi connection, would it be possible to print tickets?

No, it's not possible to print tickets while losing a Wi-Fi connection because printing by IP is available only in the case when a screen is connected to the same Wi-Fi as the printer.

You will be still able to run the POS but the printing will be stored on your device until you get into the area of Wi-Fi coverage. Then all the printing stuff should be printed.