iOS 9.3.5 is the final version for the iPad 2. While it offers better security, it can be sluggish on the older hardware. iOS 8.4.1 is widely considered the "sweet spot" for the iPad 2, offering a smoother interface, the older (and preferred) multitasking UI, and access to apps that support the older architecture.
: The animations are fluid again, and the "heaviness" of iOS 9 vanishes. downgrade ipad 2 ios 9.3.5 to 8.4.1
git clone https://github.com/LukeZGD/iOS-OTA-Downgrader.git cd iOS-OTA-Downgrader ./restore.sh # Select iPad2,x model, then option 8.4.1 offering a smoother interface