Does this work with the foil?

Not really. I found that it did pick up the foil no matter how much I rubbed the front and back of it. And then when you finally lift the foil and put it down on a surfaces, its not forgiving at all. It sticks things down right away without any ability to lift it back up and I ruined a few projects because of it. I know there was a money back guarantee on the product but when I went to their website, I was unable to find anything regarding WHERE this was to be returned I was a bit disappointed.

Can this transfer tape be used for t shirts?

Good day.this transfer tape can't work on clothes.it's easy transfer to any smooth surfaces like sign stickers, windows, walls, ceramics, glass, etc.

Is this heavy or medium tack adhesive?

Good day.This transfer tape is a medium tack. The vinyl comes off very nicely.

How long can this product be warranted?

I am not sure, I have been disappointed in this product, it does not lift the vinyl of the backing sheet with any reliability. I have ruined a couple of projects and had to start over.