You do not have to do anything special to avail Jio offer on Moto Z2 Play. Just when you start using the mobile, insert your Jio sim and it will get activated by the Jio company itself.
Yes, it does support International 4G sim cards.
Moto Z2 Play comes with Water repellent nano-coating**. Advanced nano-coating technology creates a water repellent barrier to help protect against moderate exposure to water such as accidental spills, splashes or light rain. Not designed to be submersed in water, or exposed to pressurized water, or other liquids.
No. Moto Z2 Play does not support CDMA network.
Yes, Moto Z2 Play 64GB comes with latest 7.1 Android OS so you may not require to update it immediately but going forward, company will produce OTA updates.