i have mixed up my ez pass from my other car. Will the toll booth able to detect the pass does not belongs to that car? will i get a fine?

Technically you can use in another car. Depending on the system and the state in which you use it in is whether it's legal or not. It would be legal if you have registered the other car or cars you will be using it with to that transponder. If you are switching it to another car or cars and it's not registered to it then its a risk, but the chances of you getting caught are usually pretty slim. Most of those systems are just worried about getting the toll paid.

They could care less as long as it gets paid. I have swapped tags and used them in other vehicles numerous times. Nothing ever has happened.

If both passes are on the same account, and the car you are using a pass in has been registered to your account, you have no problem. The pass is registered to an account, and multiple cars can be on that account.

I have two transponders that are on one account. I have 6 vehicles registered on that account and can use either transponder in any of the vehicles

No. But if it has trouble with the signal in any way a picture is taken and if it doesn't match what YOU said the license plate should be, you will be charged for the whole rest of the toll road.

Yes the passes are registered to the car