I just finished the walls in my basement with one inch cladmate rigid foam (The four Foot Concrete Wall ) I Have R-12 Pink Insulation In the knee ( Wood ) Covered With A vapour barrier (plastic).. I have 2 Inch Rigid Foam On The outside wall.. I built a 2x4 wall in front of the interior wall.. My Question Is Do I Need To Continue The Vapour Barrier From The Knee wall Down Over The Foam On The Concrete Wall & If I Do Will It Matter One Way Or The Other... ( I Am Getting Conflicting Stories On How It Should Be done ) ( Is The Plastic Really Necessary Over The Rigid Foam.. I already Got It Done On One Wall.)Just Wondering If I Need To Remove It Or Carry On That Way.. Does It Really Make a Difference.. Just Wondering & I Want To Do It Right.. Thanks.

I think it's as cheap to cover the 4' rigid foam with plastic as it is to tape all the seams.
I think what matters a lot is right where the concrete wall meets the floor. Often there are gaps there. I'd run a bead of tube expoxy or concrete filler along the bottom edge.
If you have an older house with nothing to keep moisture from coming up through the slab it's sort of moot.
Recent studies are showing that foam on exteriors isn't working because bugs channel all through it, and it's better to lay it flat on the ground about 2'-3' below grade. But some areas require it on the wall.