From what I have read most fruit trees these days are grown from grafts, not from seeds. The reason being is it take many years for most fruit trees to actually mature and produce whereas grafted trees usually produce within their first 5 years. Also, most seeds gathered from fruit of grafter trees will not give you the same type of tree as what produced the fruit - it will give you the type of tree that the root-graft came from. Grafts are generally used to make trees more versatile and adaptable to a wider array of regions.
So if this was an accidental seed planting by you, the previous owners, a bird, etc, etc, it may or may not be worth trying to grow for the fruit. It may be worth having if it adds to the beauty of your home. It obviously does NOT care if it is having enough sun or not since it has come back from getting chopped. And it's possible, if you didn't chop it down too low, that you did not interfere with the rootstock it is grafted to.
The only thorny trees we have are mesquite and wild plum....lol. Oh, and some sort of gum tree that I hate.... :/