but someone told me that in case of an hyd fail example(loss of green) the use of reverse is restricted only on the remeining reverse is this still true?
I would not say that it is restricted as a mandatory item. What is going to happen in such a situation is that you will not have N°1 THR reverse available. If you select, upon landing, thrust reverse on that side, the FADEC as per its logic will comand a momentary increase in idle thrust without having the benefit of a thrust reverse action. So you get more thrust in fact, when you do not need it.
Cheers.
EDIT
This is not the case when you dispatch the airplane with 1 THR reverse inoperative, as per maintenance the reverse is deactivated and you can safely apply it without having any negative consequences.