disadvantages of going to the mall等于disadvantages for going

Yes,they are same.However,of is the correct way of expression.In oral English,if y
Ou say it in your way it is understandable.
The reason you cannot replace it is advantage and disadvantage are nouns.
It is disadvantagious for ...ing is the correct expression.

1.no 2. why not,? I don't know. ha ha ha