Vauxhall Corsa corsa running then cutting out and loosing all power in accaleration.

Hi looking for some advice , My corsa 1.2 sxi 2008 Reg will drive for a certain ammount of time then cut off and it looses all power from the acceleration almost like its gone into limp mode then will cut out, when i then try turn the car on it wants to start and reaches 2,000 revs and then just drops to nothing and cuts out and also the back left reverse light stays on when the car goes like this. However ive also notice the revs sometimes seem to flicker up and down by itself when idling theres a few more concerns alongside this. has anyone had any similar problems or any idea what this could be i only passed my test 2 months ago so i dont have much idea any help would be much appreciated?