and what is the meaning of Ticket for section only?

Use the b-europe link I wrote. Nothing else will work

https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

- Lucerne - Lugano no reservations are needed, simply walk to the end of the platform where there are more seats

- Lugano - Milan no reservations are possible

You only need to add these trains to the Rail Planner app before boarding. Nothing to do on OBB

OBB would only be useful for the direct train Lucerne - Milan : 11€ seat reservation. It's best to avoid this train and travel for free

As a general advice : do not take the 12:18 train from Lucerne. It is extremely crowded and always very late as it is coming from Germany. Instead leave Lucerne at 10:18 (direct to Lugano), 11:18 or 13:18 -> both with easy change in Arth-Goldau

Please use this exact link for domestic journeys in France:

https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

That means that ÖBB can't sell a ticket or reservation for all trains in the journey. That may be because there's a regional train (REX in your screenshot: no reservations possible) or sometimes it just doesn't work when you try to book reservations for multiple Italian trains. Solution is then to book the trains separately.

@thibcabe I’m so fortunate that we have people like you who is explaining to all my questions so patiently.  Thanks a ton!

we are planning to take 2:18 pm train ..any suggestions for this?

Thank you so much for helping me with booking

That's because that page is for domestic journeys in France only. The later connections from Paris CDG airport, e.g. with departure at 18:53, there's a TGV to Strasbourg and then a regional train. You only need a reservation until Strasbourg, so only book Paris CDG TGV - Strasbourg.

I got it now :)

ok

ignore my msgs:) got it now