Place the chicken wings in a non-reactive container with a lid that will fit in the fridge.In a bowl, combine yoghurt, cumin, turmeric, smoked paprika, chilli flakes, sugar, garlic and ginger. Mix well. Add lime juice, if desired.Remove ⅓ cup and place in a separate container. Stir in 1½ tbsp (30 ml) water and refrigerate for later use. Pour the remainder of the sauce over the chicken wings and mix well to ensure that the chicken is well coated. Cover and place in the refrigerator for a minimum of 4 hours up to overnight.Prepare the curried ranch by combining all of the ingredients in a bowl and mixing well. Keep in the refrigerator until ready to serve.Preheat the grill to medium-high heat (200°C / 400°F). Remove reserved marinade from fridge and add melted butter.Remove the chicken wings from the marinade and place onto the grill. Turn often and watch for flare ups. Cook for 20-25 minutes until the internal temperature of the wings is 74°C (165°F) and they have a good amount of char, basting several times with the tikka sauce.Serve with curried yoghurt ranch dip.