St Peter's Dome with Lift Ticket

I have not used those tickets, and they are relatively new, so not sure how many have had the opportunity to do so.

Previously (and still) there is a security line in place to enter the St. Peters, Dome Climb, and Crypt area. With a timed ticket, you can use a separate line for timed tickets to go through security. So for St. Peters, yes, go to that line before 10:00 AM to get through the line and pick up your audio guide. You can do the audio tour then proceed to the elevator (located outside, on the right side of the Basilica as you are facing it.

Afterwards you are free to reenter St. Peters, wander through the Crypt, or exit.

If the regular security line is not that bad, you could really enter at anytime and go to the Basilica or Crypt, not sure how closely they police the timed entry line, maybe they would let you in at 8 or 9 for an 10:00 audio guide. Entry to St. Peters, and the Crypt are free, your ticket is only really paying for the audio guide (and the Dome climb)

FWIW: Not sure how they are handling it, maybe a third line, is entry to the area to walk through the Porta Sancta, the holy doors only open during the Jubilee year. That may add a wrinkle to the above, might be worth looking for someone directing foot traffic when you arrive.

I just watched this video that you may find helpful.

Starting at about 7 minutes 30 seconds into the video, she explains this new basilica ticket process very clearly.

Other than getting access to an audio tour, these tickets may get you through security more quickly due to the dedicated line you have access to.
It also allows you to buy the dome ticket ahead of time so you do not have to stand in that ticket line once inside.

It also mentions that the time of your ticket is more of a general guideline rather than an exact time, and that you can tour the basilica first and them do the dome or vice versa.

I went last week and the only time my ticket was thoroughly checked was when I entered the lift to go up to the dome. At the security line, they only checked that I had a ticket. However, there was no one else in the reserved security queue so they might check more when there's more people. The reserved queue is to the far right of the main queue, up against the wall; look for the people in yellow jackets/vests, they're the ones who work for the Basilica.

They'll send you an email with more details and a QR code a few days before your ticket that lays out when you should be in the queue and in the Basilica. Basically they suggest you enter the Basilica 90 minutes before your dome ticket, and they recommend you give 45 minutes for the security queue. So all in, they suggest that you enter the security queue 2h15m before your dome ticket.

I have the same reserved ticket. They sent me an email that they had to change my time and gave me a couple of options. I took the opportunity to ask if I could go up in the dome first then go into the Basilica. They responded that because of the large crowds, once you go up in the dome, you will not be allowed to go in the Basilica.

I would like to see the video link that one of the prior posters mentioned.