Using Dual Sim Cards in iPhone 12 Pro Max

I am planning to use my new iPhone 12 Pro Max to house two sim cards. One electronic sim card from my US carrier and the other one a physical sim card from a carrier from India. I need help with the following:

1. How do I make calls from these two accounts (when I am in India I would like to use the India sim card to make the call and vice versa).
2. When I do back up my data etc. to iCloud, how do I separate data from these two accounts?
3. When comes to using Messenger (text messaging) how do I keep the texts separately from each other accounts?
4. I have two WhatsApp accounts (one for India account and the other for the US account), how to download and have two WhatsApp accounts in the phone and manage it going forward.

Please help me to address those 4 points.

Thanks

Ganesh Sharma