回複：Radiology, please continue

If the I-140 was rejected, then the associated 485 must be rejected, right?

*************Right.

If I appeal for I-140 rejection, would the I-485 be rejected, therefore, would the EAD be effective during the appealing?

*************Yes, it would be. After filing appeal, you need to file a motion to reopen your 485.

It is fine to use EAD while you are waiting for appealing outcome. It happened to one of my friends here. Their appeal was sucessful.