CANT INSTALL

I uninstalled this app to try and update my phone. When I tried to download it back, it says it requires IOS 9. I can not update my phone, it just doesnt work because no matter what I do, it doesnt have enough storage. Please Ive had this app for 3 years, working perfectly! I dont understand please PLEASE LET ME GET IT BACK!

_rose_29 about Snapchat, v10.14.0.0