You do not have to pay an entrance fee, the museum is completely free of charge to visit. However, you are free to donate money to the museum when leaving and of course you have to pay in the souvenir shops and in the eating areas.

Free

You will need at least one hour for the Nero exhibit. I spent two hours there since I like to read all of the exhibit labels. You can visit the rest of the museum at any time. Since the Nero exhibit is closing soon, it may be very popular in its last week. Once inside, you can visit any exhibits you wish, except for the special exhibits that require paid tickets.

About 30% less busy but getting busier day by day

In my experience you don’t need to reserve a time but they no longer let members have priority entrance, so you will need to queue each time you visit or leave and come back. There is a members cafe/room on the first floor. The prices are still relatively expensive compared to outside.

You don't need to pay

Don't know

certamente

actually I didn’t make one and I only waited for a couple of minutes in order to enter !

No ticket. It's free.