The native Safari browser on iOS 9.3.5 is outdated and struggles with modern web technologies. If Safari crashes or refuses to load WhatsApp Web, try downloading alternative browsers from the App Store that still offer iOS 9 compatibility:
Here is why:
Apple's native messaging service remains fully functional for text communication between iOS devices on iOS 9.3.5. whatsapp for ipad 2 ios 935 updated
A guide for the regular installation method, using the ReShade Manager application...