Is this have code? how long?

I think the question is, "does this have a "cord"? Answer to that is NO. it has a plug receptacle for a three prong plug from any extension cord and that cord can be as long as you wish. When blowing the yard I use a 50ft. cord from home depot, on smaller jobs I have cord from 15ft. to 25ft.This unit works great for me so I highly recommend it.

Can my 100 year old grandmother use this and not get knocked over? She enjoys yard work.

Your 100 year old grandmother will be fine, as long as she is steady on her feet. No, this does not "KICK LIKE A SHOTGUN" - that person who said that has obviously never held a shotgun, much less fired one.

I have a smaller yard with 2 oak trees, thus a lot of leaves to clean up. Is this product strong enough to handle lots and lots of leaves?

I have 5 acres with approx. 2 doz. huge oaks with very large leaves & about two acres of lawn. I blow leaves into piles & then pick up. I use a 150 ft. ext. cord. I also use the riding mower but bags fill quick.