What kind of optimization you want ?
For optimization the answer is Yes !
The phone runs very slow, I have the last version available for it (7.1.2), I just use it for Whatsapp and Youtube, and when I open whatsapp it takes like 15 seconds to load
oh yeah i remember when i have iphone4 yea it works very slow but maybe if you reduce the number of apps you can load whatsapp faster then usual! Also , Try reducing the number of pictures in albums!
Last option : Factory Reset
But it wont work that much
Turn off Automatic Updates. Tap Settings > iTunes & App Store > and turn Updates off.
Turn off Background App Refresh. Tap Settings > General > Background App Refresh. (this option will help you to save battery too)
Also Turn off your Motion !