If some lights do not light up there might be a break in the cable or you made a mistake when crimping the connector.

For Fast Ethernet (100 Mbit/s) you only need pins 1, 2, 3 and 6. Some cheap cables may not even have more than these four wires.

G means ground. For most consumer applications up to 1GbE it should be fine if your ground is not properly connected.