What is the best way to spend alone time?

Start of your day with a glass of water.
Go for a walk/jog.
Come back home and rest for some time.
Then study something, trust me you will have very high concentration level. You can study anything from a novel to quantum physics.
Then have your breakfast.
(I suppose since you are asking for a whole day so no work/school/college)
Do something creative, write or draw or if reading is a hobby read.
Then watch a nice movie/TV serial.
Have your lunch.
Take a nap for an hour or two.
Wake up and go for a walk. Eat something you've wanted to eat from a long time.
Then enjoy the evening by calling an old friend.
Send messages to everyone who were once close to you but know you seldom talk with them.
Have your dinner and listen to your favorite song before going to sleep.

Hope this answers your question.

What's the naughtiest thing you've experienced with your babysitter?

When I was about 13 my parents went away on vacation, and thinking I was still too young to stay by myself they arranged for a babysitter who used to stay with me when I was younger, to stay at our house.

What are the best life lessons you've learned from traveling the world?

I spent my career in the Canadian foreign service. I travelled a lot but it sure wasn't for pleasure. You go some place that they send you and then you have to stay there, sometimes for years, processing visa applications.To the extent I learned anything, I was left with some views about

Can you replace your immune system?

Yes, technically you can. You can replace your immune system through a bone marrow replacement. However, this is a procedure that is not lightly considered or done. By replacing your own bone marrow with another individual's your immune system will be now derived from the other person. However, you need to