Hi All,
thanks so much for the info.
I receive a reply and as for the current state
'it is confirmed the prohibition of bringing backpacks, camping, bulky bags and luggage/trolley, but medium and small size backpacks to shoulder, which must be checked, as any other bag, with metal detectors, opened and visually inspected by the Urbe Security Institute, responsible for the entrance inspection, can be introduced.
For this reason, you have to be there at least 30 minutes before the beginning of the guided tour.'
but as Kathy said, things could change especially w/ the recent situation. i just hope that they prepare to store the bags that are not allowed if security level raised as it's troublesome for tourist not bringing a medium backpack at least.
noted for the meeting point, i need to exchange my online voucher with the tickets and they'd let me know where to go.
Also the underground guided tour is actually a complete tour with the upper level for 1.5hours. so not bad for the EUR11 (incl eur2 online boooking) fee.