An interview with the athlete - who will be sentenced for murder next month - is due to be broadcast by ITV on Friday
Oscar Pistorius has claimed Reeva Steenkamp, the girlfriend he killed, would not want him to "waste his life" in jail.
In his first TV interview since he shot Ms Steenkamp dead in 2013, the former Paralympic athlete says he would like to "help the less fortunate" if he was offered the chance for "redemption".
He adds: "I would like to believe that if Reeva could look down upon me she would want me to live that life."
Pistorius faces sentencing for murder on 6 July after his manslaughter sentence was overturned on appeal in December.
In the interview, due to be broadcast by ITV on Friday, Pistorius sobs as he recalls the moment he entered the bathroom to find his girlfriend's body slumped over the toilet.
Prosecutor Gerry Nel said Pistorius had been "disrespectful to the court ... to the victims ... and the deceased" in talking to media but not testifying.
Ms Steenkamp's father has said the murder of his daughter "devastated" his family and that Pistorius must pay for his crimes.
The former athlete has consistently denied murder, saying he thought an intruder had entered his house in the early hours of Valentine's Day 2013 and that he feared for their safety.
Prosecutors have argued that Pistorius intentionally killed Ms Steenkamp after an argument and said he had shown no remorse for his crime, feeling sorry only "for himself".
At his original trial, Pistorius was found guilty of culpable homicide (manslaughter), and was sentenced to five years under correctional supervision, of which he served only one in prison.
For the past eight months he has been living under house arrest at his uncle Arnold's home, and in the interview Pistorius describes the difficulties he has faced to integrate back into society, "being infamous and famous".
He is asked about his possession of firearms, and admits to owning up to 11 guns - though he says only one was kept at his home.
The South African also demonstrates walking without his prosthetic legs, and says he could not have run away or defended himself from an intruder while on his stumps.
Arnold Pistorius has insisted it was his decision and not his nephew's to do the interview and that no one from the family would profit from it.
He said in a statement: "I decided it was necessary to take up one media offer that would provide our family with a voice to address some of the misconceptions that have remained unchallenged."
In South Africa, murder carries a mandatory minimum sentence of 15 years, though a judge may deviate from this in "substantial and compelling circumstances".
Speaking to Pat Kenny last year, Reeva's mother June said: "I've got no feelings of revenge or wanting bad things for [Pistorius] - I'm just not like that, I have to move on with my life."