talk about if XXXX?
1.they are talking about if OR talking if dealth penalty should be abolished.
2. they are talking about the abolition of dealth penalty.
Questions:
(1) for 1, which one is correct?
(2) are 1 and 2 the same thing?
(3) It depends on how you use it. or it depends how you use it?

Question

talk about if XXXX?
1.they are talking about if OR talking if dealth penalty should be abolished.
2. they are talking about the abolition of dealth penalty.
Questions:
(1) for 1, which one is correct?
(2) are 1 and 2 the same thing?
(3) It depends on how you use it. or it depends how you use it?

Answer

1. They are talking about whether the death penalty should be abolished.

2. No. Sentence 1 means that the death penalty has not been abolished and the possibility of abolishing it is still hypothetical at this stage.
Sentence 2 suggests that 'the abolition of the death penalty' is an event which either has happened or might  happen.

3. Both are correct. The 'on' can be omitted.

NB. Note my corrections to your sentences. You need to say 'the death penalty'. You cannot omit the article. This is a definite noun phrase referring to a particular type of penalty, so the definite article is needed. Also, don't forget to start each sentence with a capital letter.