Hello there!
As you may already know, the iOS 9.3.4 update is the latest version that Apple has released for users. While it doesn't bring significant improvements compared to the previous version, iOS 9.3.3, it does enhance the quality of use and security measures for users.
Should you update your iPhone 4s to iOS 9.3.4?
https://Mytour.vn/co-nen-nang-cap-ios-934-cho-iphone-4s-khong-5494n.aspx
If you're considering updating your iPhone 4s to iOS 9.3.4, we advise against it. Despite your device still being listed as capable of the update, the hardware limitations prevent smooth operation post-update. In a brief test conducted by Mytour.vn, it was observed that using an iPhone 4s with iOS 9.3.4 leads to some system apps not performing optimally, including the default Safari web browser. Considering your iPhone 4s, we recommend sticking with iOS 7.1.2 or 8.4 as the versions where your device can perform optimally.