If my Mewtwo attacked with "Barrier" last turn, and this turn I retreat it and use Switch to make it active again, can I attack with "Barrier" again?
No. The prohibition against using Barrier if it was used last turn is not an effect, it is a Game State check. So it can't be cleared by moving Mewtwo to the bench.
Source: Evolutions FAQ (2016-11-03), TPCi Rules Team (2016-11-03)

Relevant cards

Note: All applicable cards may not be listed below.
XY12_51