iPhone 4 please help :(

My uncle gave me one of his "broken" iPhones. Well when I got home that day I tried to power it on and the battery to wall charger came on the screen so I plugged it in and it stated charging so I left and came back to get it to watch my brother play video games in his room and when I plugged it in nothing happened. I eventually got it to work and one night I fell asleep listening to music on it and when I woke up there was water or something wet on it. The flashlight was flickering high and low like the battery was dying it was hotter than **** and no music was playing. I got up and went to the bathroom, got something to eat and came back and the light was not flickering it was still VERY HOT literally I could not pick it up it was so hot. So I put it on the charger and held the home and power buttons down to try to hard boot it but nothing happened like all the other Times it froze. My sister was playing with it a couple of days ago and banged the back of it into a corner or something and broke the back glass and I would try the rice thing butt one screw is stripped and I can't get it out to take it apart. If you have read all of that and can giver any tips or tricks on how to fix it or if can be fixed. PLEASE!!