The Hall of Mirrors at Versailles is great, and the interiors are stunning. I went in 2017 when I spent 10 days in Paris, and I still felt the trip was too short.
On restaurants, here are some of my recommendations, which include a fancy spot or two if you can get a reservations.
MoSuke (https://mosuke-restaurant.com/en/home/)- This is my favorite restaurant from my last trip in 2022, and it has been one of the hottest reservations. The food is incredibly well done. I actually finally got back to writing up my trip (I know 1.5 years after the fact), so will have that posted soon and will link it here. The Chef, Mory Sacko, has another restaurant in Paris now too, Lafayette's. https://www.lafayettes-restaurant.com/. As an aside, I liked MoSuke so much it is on my list of places in Paris to revisit next time I go.
Montee (https://restaurant-montee.fr/en/) - One of my favorite restaurants in Paris, the lunch menu is an especially good deal. (https://www.mlleshetravels.com/home/tags/restaurant-review)
Ok, so those are the prix fix places.
Josephine Chez Dumonet for French Classics. The boeuf bourguignon is outstanding (Eater says best in the city, and it is very, very tasty) as is the pigeon millfeuille. Also, Grand Marnier souffle is a must. Here are photos.
Les Parisiens is on my to go to list, so I wanted to include it here. Folks that have been have raved about it. https://en.pavillon-faubourg-saint-germain.com/restaurant-les-parisiens
Chez L'Ami Jean - Everything is outstanding. The rice pudding is to die for.
Le Chardenoux - Beautiful little place by Cyril Lignac. I went on my last trip. The photos are here... (https://www.mlleshetravels.com/single-post/2022-paris-trip-a-real-and-surreal-journey-on-day-2-in-paris)
Bistrot Paul Bert - Steak Frites. Do it.
Le Servan - Absolutely excellent restaurant by two sisters in the 11th. French with influences from China.
La Tour Montlhery - Chez Denise - The cote de beouf and the lapin a la moutarde are all great, as are the escargot. Oh, and chocolate mousse.
Le Dauphin (same chef as Le Chateaubriand) is a great wine bar with smaller plates next door to Le Chateaubriand. Have had a lot of amazing food there (and I believe posted about it on the old site). Also all the Avant Comptoirs are really good. Same concept, small plates, great wine, next to Le Comptoir.
I have a number of places on my to go to list for next time as well, besides Les Parisiens, so I will pass those to you:
Petrelle, Parcelles, Les Arlots, Papillon, Le Truffaut, Coretta, Granite, Frenchie, Juveniles