Hey Fabio!
Happy to answer these questions, though a bit out of order as follows:
Does this plugin allows WooCommerce to sell tickets as products?
Yes! Tickets are of the “products” type within WooCommerce.
My hostess at the event will scan the ticket that customer prints or displays it on mobile screen. Is there a mobile app that does that?
Yes! There are ton of free apps out there for Android and iOS devices — we don’t specifically recommend or endorse any specific one, but if you search for “QR Code” in any smartphone app store you’re sure to find a ton of good, free options.
If so, does this app automatically marks this ticket as “checked in”, preventing a re-use of the ticket?
Yes! Once checked-in, a ticket is marked as such and cannot be re-checked-in. One ticket = one check-in for that ticket only.
I hope this info helps; please let me know if there are any other issues or questions I can try to help with.
Sincerely,
George