Trains – Combine the Navigo Pass with a SNCF point-to-point ticket

EDIT: I have misread your question, your assumption is incorrect. See below

On the first question, your assumption is not correct: weekends are "unzone" periods in which your 2-zone Navigo Pass can be used for all zones within the Navigo zones. Other "untouched times" are holidays, school holidays for Ile-de-France and in summer (mid-July to mid-August). Source. NOTE: This is Only valid for the monthly ticket, these does not apply to the weekly ticket,

EDIT: does not allow you to use the pass for destinations outside the Navigo tariff zones. The suspension is only relevant to the 2-Zone Pass that you can purchase (by opting out of the All-Zone Pass).

The second question does not prevent you from doing so and you save money by using this scheme. Just make sure you have enough time to get the new ticket, as some destinations are overcrowded and you may have to wait up to 10 minutes before you can buy a ticket. This is called a "complément de parcours" source

vpn – IP Sec over Internet or point-to-point dedicated connection. Which is safer and cheaper

There are two branches in my network, and the branch should be able to access the central office network. There are two options for me and the first one is ipsec vpn through the public internet and the second option is point-to-point dedicated VPN connection.

My branch has the DR site, and all the high availability servers are in the branch.

Please let me know which is flexible, cost effective and secure. How do I choose the best option for my requirement?