Rub lamb with Greek seasoning. Refrigerate, covered, 2 hours. In a shallow bowl, whisk vinegar, oil, lemon juice, soy sauce and garlic until combined. Add lamb and turn to coat. Refrigerate, covered, 4-6 hours or overnight, turning once or twice., In a small bowl, mix mint, jelly, and hot water until combined. Refrigerate, covered, until serving., Drain lamb, discarding marinade in dish. Cover rib ends of lamb with foil. Grill, covered, on an oiled rack, over direct medium-high heat 2 minutes on each side. Turn; move to indirect heat. Cook, covered, until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°), 25-30 minutes longer. Let stand 10 minutes before serving with sauce; sprinkle with fresh oregano and additional fresh mint.