can it grab items in kitchen that are hard too reach?

Yes it can. I wouldn't pick up a dinner plate with it but you can reach for the salt or a can of veggies.

does this hook on a wheelchair?

if you have a 10"' piece of ribbon, cord etc. put it into the hole in the reacher handle, make a knot, then hang it onto your wheelchair handle.

Is 26" reacher measured by just the shaft, not including handle, or is the whole reacher 26" long including handle, etc?

The measurement of 26" includes the full handle -

Some of these reviews say that the reacher is not good for heavy objects. Would I be able to pick up a wet towel or a running she off the floor? Thank

Only if they were rather light. There are far better tools out there. The garden tool section in home centers have sturdy tools and you can try them out for grip, balance etc.. Pick up tools are like those running shoes. You really need to try them out and find what works for you. SP makes the best hand thumb brace I ever used (must use a left hand brace for the right hand though). That was why I bought their pick up tool but was very disappointed with it. It is no where near the quality of their braces.