Clarify Paris airport train ticket?
I am traveling to Paris this month for the first time since 2000 and, while I understand how to purchase metro tickets on my phone (I have the app downloaded), I want clarification on the special tickets to get to and from the airports- the recommended route for me to get from the hotel to Orly to pick up our rental car (we are going out of the city for part of the trip so I will be leaving for the airport from the city) has me start on the metro, taking the 12 train from Jules Joffrin, and then switch at Saint-Lazare to the 14 Aéroport d'Orly train. Do I need a separate, regular metro ticket for the Jules Joffrin-to-Saint-Lazare leg, and then use the airport ticket starting at Saint-Lazare, or will the airport ticket cover me for both the 12 train and the 14?
Likewise, on the way in from CDG, will the airport ticket cover me from the airport to the Simplon station, or do I need a separate metro ticket, too? In that case, I'm switching from the RER to the metro at Gare du Nord, I believe.
And huge apologies if this is a dumb question; getting tickets for the metro and RER have clearly changed since I was last there and I'm trying to understand how to get tickets correctly and not end up getting fined for doing something wrong!