How are you able to send whatsapps to people you don't have a prior conversation with ?

I am doing the same boat...and was working fine until i lost & replaced my old phone. All conversations were lost, and this makes it challenging to use whatsapp for any non-group conversations (since I can't start any).

You can start a conversation with any WhatsApp number by opening the url wa.me/number. The number must include the country prefix.

There are also some apps and webpages that helps with this process (Disclaimer: I'm the author of one of them for Android [0])

[0] https://play.google.com/store/apps/details?id=com.trianguloy...

Others can still allow access to their phone book and the information stored in them about you will be transmitted and saved at Facebook, won't it? Is there a way to disable that?

Exactly this. I recently started a twitter for my academic career. Didn't share my contacts or anything (I only follow academic twitter too). I get tons of suggestions of people I know and several have followed me. The information is from their contact list because twitter knows my number and connected us. There's a clear benefit to this, but there's also privacy concerns too. The lack of control over this is what is concerning.

> Is there a way to disable that?

No.

You need an account to ask FB to delete your data.

Last time I tried (a year ago or so) I couldn't add new people to chat to. They had to contact me first.

As I've seen on WhatsApp on every smartphone I've had: when you download WhatsApp and tap the "New chat" icon in the upper right corner, the app SHOWS YOU a list of everyone from your phone's contact list who has a WhatsApp account. They also show the list when you click "Chat" at the bottom and then "New Group."

Without Contact access in iOS, WhatsApp blocks you from starting a group chat, but allows individual chats.

You can't start a group chat, only individual chats.