Answer to my question 4 and 5

Q4.What kind of ways are there for death penalty?

Animals　ex.Crushig by elephant
Back breaking
Garrote (abolished)
stoning
Hanging
Shooting
Lethal injection
electric chair
boiling
Buried alive
burning
cooking
crushing
Poisoning
Gas
Crucifixion
decapitation
etc.
These are some ways that i have found. However there are more ways as it was done a long time ago and some are abolished so it was hard to research all the methods of death penalty.
The most common way is hanging and lethal injection and eletric chair.

Q5.How many are there?
As you can see from uestion4, it is hard to tell the exact number of the methods.

<http://www.neatorama.com/2007/05/29/this-wont-hurt-a-bit-a-painlessly-short-and-incomplete-evolution-of-execution/>

<http://www.clarkprosecutor.org/html/death/methods.htm>