How to say throw away: 扔掉?
1) Is 扔掉 the formal way of saying "throw away"?


Yes, it is. 

'掉' in  '扔掉' is a result complement, not a verb itself.


  2) Is there a difference between using 扔 or 掉?



扔 mainly mean 'throw'
掉 mainly mean 'drop' 


you can 扔 forward, backward, upward or downward; But you can only  掉 downward