train 9862 (Lyon to Paris) - does it have duplex cars?

I believe this is a single deck train. Here is a seat map, showing the seats as facing each other in carriage No 6.
https://www.seat61.com/reference/trainseatplans/tgv-reseau.pdf

You can't choose seats in second class, only in first class. Second class seats are assigned by the computer. I usually travel in 1st but I believe in second you can check mark a preference for a 4-seat arrangement, especially if all tickets are on the same purchase. The above seat map is for first class because it's three across. Second class has four across but still has the four-seat units as shown on the seat map..

The above seat map is for first class because it's three across

Well Elizabeth, I guess you did not notice that the document I linked has 2 pages. Page 1 is 1st class carriages (No 1-3) and page 2 has the bar car and 2nd class carriages (No 4-8).

Thanks Sam. I didn't. I see it all now.

But OP are you sure about the train number because the SNCF bot didn't have train 9862 for July 12th. You can ask the bot on the bottom of the SNCF page.

I know you can't choose seats with 2nd class, but I thought there would at least be an option to choose upper or lower. On a dry run through the booking process, eventually it tells you the seat numbers and train number - it shows #9862. I captured it here: https://jagbev.ca/_temp/9862.jpg

I don't see any bot or chat at the bottom of the page that might tell me the train number.

Train 9862 is a train to Brussels calling in Paris at Chessy and CDG.

When in doubt about a train composition look at the vagonweb website.
It is generally a single deck TGV Reseau- 2 x 10 car single deck sets coupled together.

Infrequently it can be a double deck and a single deck set coupled together.

Thanks for the link to vagonweb.cz - another amazing site (along with seat61)

Train 9862 is a train to Brussels calling in Paris at Chessy and CDG.

But 9862 is also my train from Lyon to CDG.

From vagonweb.cz:

• Montpellier Sud de France 9:12
• Nîmes Pont du Gard 9:30-9:33
• Valence TGV Rhône Alpes Sud 10:10-10:15
• Lyon Part Dieu 10:50-11:00,
• Marne la Vallée Chessy TGV 12:45-12:50
• Aéroport Roissy Charles de Gaulle 2 TGV 13:01-13:08
• TGV Haute Picardie 13:34-13:38
• Arras 13:55-14:03
• Lille Europe 14:25-14:52
• Bruxelles Midi 15:26

The times match what I see on SNCF (11:00 at Lyon Part Dieu, 13:01 at CDG), but I'm not sure about "Marne la Vallee Chessy TGV" in between, because SNCF clearly shows "direct" with no stops between. It doesn't really matter to me.

"Direct" means no train changes, not non-stop. Trains stop all the time. Your's stops at what is essentially Disneyland Paris.

SNCF clearly shows "direct" with no stops between

Yes, "direct" just means you do not have to change.

You can confirm if you search on the SNCF Connect website for a trip from Lyon Part Dieu to Marne-la-Vallée - Chessy on that same day -- you will find the exact same train (9862) offered for a trip that leaves Lyon Part Dieu at 11:00 and arriving at Marne-la-Vallée - Chessy at 12:46.

Thanks for the clarification. We'll wave at Le Mickey as we go by.

So it’s the train to CDG, not to Paris. It’s single level. I’ve taken it to the airport before.

Yes, CDG. Sorry for not being more clear.