AF4083 is not a normal flight number. I guess it's a rebrand of the return sector of the second attempt at AF136, which is currently crossing the Atlantic.

Since it's an involuntary re-route, I would expect AF to refund the cross-city transport. But they won't organise it for you, you'll need to claim back after.

With the new extension to metro line 14, you can get from CDG to ORY with a change at Chatelet-Les Halles, in about 75 minutes. I think this is somewhat faster than the change at Antony to the Orlyval shuttle, but Chatelet is a super busy transfer station. Antony in contrast very easy to navigate.

If you have a lot of luggage or not a lot of time I would consider a taxi.

I don't know the reason AF136 returned to CDG, but would guess it is not medical or weather. So should be a good chance for EU261 compensation. In any case duty of care applies, so keep all your receipts and launch a claim at the completion of your trip.