What is the Du`a (supplication) of Istikhara (guidance prayer)?
O Allah, I consult You as You are All-Knowing and I appeal to You to give me power as You are Omnipotent, I ask You for Your great favor, for You have power and I do not, and You know all of the hidden matters. O Allah! If you know that this matter (then he should mention it) is good for me in my religion, my livelihood, and for my life in the Hereafter, or he said: "for my present and future life" then make it (easy) for me. And if you know that this matter is not good for me in my religion, my livelihood and my life in the Hereafter, or he said: "for my present and future life" then keep it away from me and take me away from it and choose what is good for me wherever it is and please me with it."
Can I start fasting based on the moon sighting of another country?
You must follow the moon sighting of the country you are in.
Should missed Sunnah prayer be made up?
Making up missed voluntary acts of worship is from Sunnah.
What is the ruling on insulin injections?
Insulin injections do not break the fast because they are administered under the skin and do not reach the body cavity (jauf).