Harry came back because Voldemort had used Harry's blood to regenerate. The protection that Lily's sacrifice provided to Harry got redoubled and now ran in both Harry's and Voldemort's veins. Thus, when Voldemort cast the killing curse on Harry, it didn't work properly. It only destroyed the horcrux inside Harry.
Dumbledore left Harry the Resurrection Stone (disguised in a Snitch) in his will, and Harry uses it just before he goes to battle Voldemort. However, he doesn't use it to try to bring the dead back for an extended period or anything.
Harry wasn't trying to bring back his loved ones so that he could live with them again happy ever after. He wanted them for comfort and moral support while he walked to what he sincerely believed was his death. He used it in an unselfish way.
As per Dumbledore, Harry was the most selfless person he knew. And Harry even demonstrated this in first part, where he wanted to find the stone but only to keep it safe, not wanting to use it. And after his death, Dumbledore wanted it to be safe. Maybe that's why he left the stone to Harry.
Sticks of Butter to US Cups and GramsBUTTER VOLUMEUS CUPSGRAMShalf (1/2) stick of Butter1/4 cup56.7 g1 stick of Butter1/2 cup113.4 g2 sticks of Butter1 cup226.8 g4 sticks of Butter2 cups453.6 g
Ounce to Stick Of Butter Conversion TableOuncesSticks Of Butter5 oz1.256 oz1.57 oz1.758 oz2
On average there are 10 feet per floor of a building, so 10 times 50 stories equals 500 feet. That depends on the structure of the building and the total height of each floor. Typical height of a 10 Storey building is 100–110 feet. Typical floor thickness is 6 inches.