whatsapp from unavailable iphone

You don't, you need to backup before your phone becomes locked.

To unlock your phone, you will need to reset it. Unfortunately your data is already gone.

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

Click on the link for instructions on how to reset your passcode without a computer if you have iOS 15.2 or higher.

How to remove your iPhone, iPad, or iPod touch passcode without a computer - Apple Support If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

Click on the link for instructions on how to reset your passcode using a computer.

If you forgot your iPhone passcode - Apple Support If you forgot your iPhone passcode - Apple Support

AJY_MAS wrote:

i never backup whatsapp. how to install whatsapp to anothe iphone and restore whatsapp without losing any whatsapp data

My experience says that is not possible after your device is disabled due to forgotten passcode.

No, there is no other solution.

WhatsApp is not an Apple product. Contact the app developer here --> App Support or WhatsApp FAQ  Or Restoring your chat history - WhatsApp FAQ or Contact WhatsApp

WhatsApp Business is not an Apple product. Contact the app developer here --> Developer Website  or App Support  or WhatsApp business products - WhatsApp FAQ