Day in Florence

I would think the Duomo museum alone would take 2 hours, unless you are just doing a walk through all the rooms (in which case, what's the point). The Duomo likely an hour.

While it may be possible to visit all these places if you carefully limit your time at each one (rather than taking your time to absorb all there is to see), it sounds positively exhausting.

If you have 4 days in Florence why are you trying to cram all this into one day?
Sounds exhausting

Doing day trips to Bologna and Venice. Will have two full days to visit sites in Florence. Can do some of the above on the second full day, but also want to visit San Miniato Al Monte, Piazza Michelangelo and Palazio Vechio.
Upon reflection, will likely allot three hours to visit Duomo Complex and at least two other sites in afternoon the first day. ,

On our visit in Oct 2022, the Duomo line was VERY long, and I assume it was for those ticketed for entry. I'd guess 45 min to get IN to the Duomo. We spent at least 2 hours in the Duomo Museum, which has all of the important pieces (like the doors). We did not go in to the Duomo. One other option to the Duomo is to find out if there is an early Mass. These are often in a small side-chapel, since almost no one goes to Mass anymore. That means that you can walk up and just go in.

Even if you are physically able to see all those sights in one day, they will totally run together in your memory. Florence is my second favorite place I've ever been, but your plan doesn't sound like fun at all.

For our visit to the Duomo Museum ( May ), there was no line.

A day trip to Venice.
That's (at least) 5.5 hours on the .
Agh
I'd bail on it and have a relaxing day in Florence.

Venice is a great city to visit. If you only have a day then do it but if you can stretch Venice to 24 hrs. that will give you a better look at this lovely city.

A day trip to Venice is foolish. You will hate it. It requires at least 3 nights. We are here now and staying 4 nights. And it’s our second time here. Florence was packed.

If you really want to do a day trip to Venice: Go! I did this some 20 years ago while in Italy for a week with my then-teenaged daugher. We only had a week in Italy and really wanted a day in Venice. Looking at Trenitalia website today, the freccia (fast) trains take approx. 2'15". If you leave Florence at 7:20 am and return leaving Venice at 7:36 pm, you could have ten glorious hours in Venice! Do make your reservations ahead of time, because these tickets sometimes sell out a few days ahead (although pre-booking takes the risk of being in Venice on a rainy day).

@mosesrus: Is this trip intended to be a quick scouting trip to plan future visits, or are you intending to see everything you can as you won't be back for awhile? Different answers likely for either scenario. With that caveat:

You previously posted on what looks like this same trip, and had an Airbnb planned for Venice, 4 nights. I assume your plans changed? That was a better option. As noted by others, I feel trying to do Venice in a day is not in your best interest. You will likely arrive the same time thousands off-load from their cruise boats. Trying to see the sights in competition with them and the "un-normal" crowds this summer could be a real mess. "Avoid-crowds.com" shows boats in port almost every day thru September except Sunday nights with +2500. My wife and I were there in April for 4 days/5nights and didn't immerse in everything we wanted to. I wouldn't recommend doing Venice in a day. Plus evenings are spectacular with perfect lighting and less crowd.

Florence in essentially 2 days (plus your day trips) will be a rush-rush to barely experience it. We've been twice in the last year shoulder season, 4 full days/5 nights each, and still have lots to see on another trip. Trying to fit everything you have listed in one day? You could easily spend more time in line than seeing the venues.

Specific to your questions, with the caveat I don't know your expectations in visiting historic sites:

"is two hours enough to visit the four sights?" - No. In April the Duomo had a line past the front facade and around the north before the doors even opened. The line and entire piazza was packed all day.

"visit the Medici Chapel on timed entry" - You will enter via the crypt and through the Cappella dei Principi to get to Michelangelo's chapel. The Cappalla is possibly the finest example of architecture I have ever experienced. We spent 2 hours there alone, and it will be a must see again when we return. Maybe it's not of interest to you.

"Santa Maria Novella list of 90 minutes" - That sounds about right. Though be aware if you are expecting a walk-up ticket you might want to be there just prior to opening - 9:30? - as we walked right in. Other times during the day had a very long line. And it's closed for services - check for opening times.

No Uffizi, Pitti Palace, Accademia, Bargello, Santa Croce, Mercato Centrale, Ponte Vecchio?

We pack our days when visiting Europe, but as someone else noted, your trip makes me feel exhausted.
Good luck with the crowds. Enjoy.