Should I upgrade my iPhone 4? - 1

My contract for two years has finished.
And my phone is okay, but there are several issue:
1. My iPhone 4 battery sometime can suddenly turn to zero even though I charge it already,
or maybe the battery has 40% yet it suddenly lost it's battery.
2. My iPhone 4 has 2 times lost it's battery power and you can't turn it on
3. My iPhone has two can't open even though I charge it already
4. The sensitivity of the touch sometime can be off maybe because of the crash
or bug of the apps
5. Some apps have some crashes

I'm still using the latest iOS 6 though, sometime Facebook or Safari can crashes

Do you think I need to upgrade or change my iPhone 4?
or I just need to change my battery that will cost 80 bucks?

What phone do you recommend?
iPhone 5s or some Android phone like Sony Xperia Z1 or HTC One or Nokia Lumnia 1020 or 1520?
I don't like Samsung though

Should I stick to iOS or change to Android or Windows or maybe Jolla Phone?

thanks

Added (1). or maybe I should wait for iPhone 6? But I doubt about the screen size

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