No Network,the front camera doesn't take color picture and the flash

I've bought a fairly used iPhone 4G but found that the phone doesn't recognize network signals although the bars will be present but there wouldn't be any network logo and it will not receive any signal.

The front camera does not take color picture, as I only saw hazy pictures unlike in my friends iphone.

Pictures taken with rear camera with flash appear hazy white, although the flashing comes out normally.