Answer to my question 1

How many people have died from the death penalty?

It is quite impossible to know the exact number of the people who were executed.
This is because of the policy in China where the infomation of death penalty is not revealed. It is estimated that at least 2,466 people were killed.
However, the number does not count the number in China.

I was quite shocked that the number could not be clear and that there were countries that would not reveal how many people have been executed even though it is a serious probem. The people in their country should at least know the informaton and consider the fact that there are alot of people being executed.

The number of people varies each year but in 2014 3 people were executed in Japan.

I've got the information from a site called Amnesty International, which is a NGO that supports human rights and abolishing death penalty.
And another site where it covers the data from 1945 to 2015.

"死刑廃止 - 最新の死刑統計（2014）."Amnesty International,1 April,2015, 22 July 2015.
<http://www.amnesty.or.jp/human-rights/topic/death_penalty/statistics.html>
"死刑執行・判決推移", 22 July 2015.
<http://www.geocities.jp/hyouhakudanna/number.html>