Nothing
Not possible.
No, the use of the gps which the Find My iPhone would use draws battery power. Therefore, if you don't have any battery left, you can't use the gps
No, the iPhone 5c battery is not the same as the iPhone 4 battery. The iPhone 5c uses a different battery model with a higher capacity compared to the iPhone 4. Additionally, the physical dimensions and connectors of the batteries are also different, making them incompatible with each other.
Look for it
The Apple iPhone 6 Plus has a better battery life than the Apple iPhone 6.
a battery
1432 mah battery
Because Macintosh rushes all their products, and they never bothered to design a decent battery cell for it.
Either the battery has a dead cell, which will require you to replace it, or something is on pulling power from the battery. Disconnect the negative cable and leave it off overnight. If the battery is dead the next morning the battery is defective. If not, then find out what is pulling power from the battery. Ignition switch may be defective.
take to a iphone store
take out the battery pack and put it back in
The iphone 4 does have a removable battery, but it is difficult to take out and not a typical cell phone battery that you can just pop in and out. It is possible to remove the battery from an iphone 4, but not an easy process. It requires you to pretty much disassemble the whole phone.