These questions are normally asked to assess various abilities of the person, largely goal orientation, handling difficult situations, and to check if the person can think on his/her feet. Having worked in HR for so long, if someone asks me these questions now, my answers would be:
What do you want to do in your life? - Be happy and create happiness.
Which was your toughest time in your life? - Yet to come... probably the current moment... convincing you that I am the best person for this role.
Was there anything in your life you wanted to do and would always regret that you did? - Flirting with values.
What is the most difficult task for an HR person in a lead role? - To lead.
Why is HR required? Can it be always outsourced? - Yes, one needs a good HR person for effective HR outsourcing.
Why are you here? - To seek an opportunity to make a difference in your life/organization.
Having answered these, I would STRONGLY recommend that everyone should have their genuine answers. A genuine response makes a difference. The human mind is great; it immediately senses the mugged-up/superficial answers. So, do not try to copy phrases of others; create your own with sincerity, and you will see that it shall work.