Are small bits of cooked leftovers frozedn separately in plastic bags safe to use after about 1 and 1/2 years?

Safe? Probably. Nutritious? Not as much. Palatable? Not on your life! After that amount of time the cell structures break down, the freezer pulls out moisture, and you're left with lifeless, freezer-burned food that tastes like an old freezer and offers little in the way of nutritional value.

Tell your garbage can to open wide....

Not after that long - a few weeks is long enough to keep them, after that nutritional value and taste are likely to decline rapidly.

I wouldn't use them, because they probably have freezer burn and have lost all nutritional value. Things like that should be used within six months of freezing them.

Probably not very good after that length of time. I would just throw them out

No.