Could someone please advise on how to take train/subway to Badaling of Great Wall from Tiananmen.

1. I suggest you walk from Tiananmen Square to Qianmen metro station to take subway line 2 to get off at Xizhimen. Then walk to BJ North Train Station, where you can take a direct train to Badaling in an hour and twenty minutes.
2. Yes, cable car service is available at the great wall to take tourists to the top of the wall.
3. After visiting the Great Wall, you can take bus no. 879 to Changling or Dingling, which is a part of Ming Tombs.