Q 1: I am a merchant. Someone asked me to buy him a certain commodity. He did not give me money.
I bought this commodity he asked for and gave it to him.
Should I ask him for the agreed upon price or can I increase the price to more than what I paid for it?
You have to tell him the price you paid for this commodity, and you may ask him for an increase in return for the efforts you exerted in buying this commodity.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.