Commented: Grafting grapefruit on lemon treeThis is definitely possible, I would try 't budding' first though.
Here is a link that might be useful: Grafting Citrus Together
Commented: What is the best way to germinate apple seeds?Justin, in my years, i have found that the moisst paper towel and plastic bag method in the refrigerator for a few weeks works best. Good luck!