4.How to judge your Pi works OK

Method one.See from the flash RPi LED

When the raspberry pi work, You will see a red LED lighted and a yellow LED flashing.
See video
If you just see the red LED and the yellow LED not flash,You need to reburn the Raspbian OS or try to change a new SD card:

Method two.With a Raspberry Pi LCD
Generally You should see the following picture after the right boot:

If you get this following picture or similar phenomenon

You should reburn the Raspbian OS to your SD card