Scavi tour and Friday night Vatican tour in one day

"The Vatican" is the entire area and is made up of many different buildings and locations. I believe you are referring to the Vatican museums which are part of "the Vatican".

No, your scavi tour ticket does not give you entry to the museums. They are separate venues within the Vatican. Your scavi tour ticket will give you entry to the underground and end just outside the basilica. You may then enter the basilica without needing to wait in the security line for it. After the basilica I would suggest getting lunch or dinner and then visiting the museums that evening. You'll need to book entry tickets for this as you don't seem to already have them.

Donna

"Also does our admission ticket for the scavi tour gain us free access to the Vatican if we do it on our own?"

If by "the Vatican" you mean the Vatican Museums (where the Sistine Chapel is), then no; there is no free entrance to the Vatican Museums. You must buy a separate ticket.

St. Peter's Square and the Basilica are the only parts of Vatican City that are free to enter. Other parts either require tickets, or are off limits to tourists. More detailed explanations and links to buy tickets are in this thread: https://community.ricksteves.com/travel-forum/italy/fast-track-vatican-museum

Thanks for the advice, I so appreciate it. We will buy our Friday night Vatican tour ticket separately. So looking forward to it.