Q.A tree i got from my mother.
Mom said it was a lemon, but I’m not sure. I think it’s a lime. It has large sharp thorns. the fruit is green but eventually turns yellow. What is it?

Certified GKH Gardening Expert
Almost all varieties of citrus, including lemons, limes, and oranges can possess thorns. It is very common for a lemon to start green, as is all citrus, and then turn to its color. I believe what you have is a lemon. Here is an article for more information:
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm