What is the minimum number of volts needed to make a reaction happen

Refer to this cell for questions 1-3: Apply a current to an aqueous solution of potassium bromide. Use inert electrodes.O2 4H 4e –> 2H2O 1.23VBr2 2e –> Br- 1.07 V2H2O 2e –> H2 2OH- – 0.83VK 1e –> K -2.93V1. What is the minimum number of volts needed to make a reaction happen?2. Which of these reaction will happen at the cathode? (Choose a b c or d)a) K 1e –> Kb) H2O 2e –> H2 2OH-c) 2Br- –> Br2 2ed) 2H2O –> O2 4H 4e3. What is the net equation for this cell?