The time turner couldn't have been used to save Harry's parents because it was too far back in time; you cannot go back more than five hits without there being very bad consequences.
With the established Harry Potter time travel rules, Harry and his friends never had the option of traveling back in the past to kill Voldemort. If they were to do so, Voldemort would already be dead in the present timeline.
Because it's too dangerous to go further back than a few hours. Why didn't anyone use the Time-Turner to save the lives lost in the final Battle of Hogwarts? Because by that point, no more Time-Turners were left in existence.
Harry Potter obviously could not return to Hogwarts, as he would have been given to Lord Voldemort before he entered the doors. Regardless, Harry chose not to return as he was searching out Lord Voldemort's Horcruxes.
Why couldn't Harry use the Time-Turner to save Sirius?
He wouldn't have thought about using Time-Turners. Sirius would resist. If Harry appeared randomly and tried to save Sirius, he would be suspicious of some kind of Dark Magic. Or, if he didn't get suspicious, he would turn the tables and try to protect Harry, at which point nothing would be different.
Why Harry Didn't Die in the Forbidden Forest Explained (Canon)
Why didn't Harry go back in time to save his parents?
The time turner couldn't have been used to save Harry's parents because it was too far back in time; you cannot go back more than five hits without there being very bad consequences. They saved Buckbeak because he was about to die three hours before.
Why didn't Hermione use Time-Turner to save Sirius?
In POA, Harry did save Sirius with a time-turner only. However he could not do the same in OOTP because using a Time-Turner would have meant going back in time and interfering with established events.
After the war, Ron became an Auror and helped reform and revolutionise the British Ministry of Magic. After two years as an Auror, he went to work at Weasleys' Wizard Wheezes with his brother George. He and Hermione eventually married and had two children, Rose and Hugo Granger-Weasley.
Honestly, Hermione knew Dobby was a lost case... nothing could have revived Dobby after the attack or she would have definitely helped Harry with Dobby considering she was the girl who started S.P.E.W(Society for the Elfish welfare) and fought for elf rights. There was nothing to be done at that point.
Why didn't they just use the time turner to stop Voldemort?
In conclusion, Harry couldn't go back time and kill Voldemort because of the Novikov's Self-Consistency principle and how the Time-Turner works in the Predestination Timeline.
Voldemort believed, out of his lack of understanding love, that by using Harry's blood, it would allow him to bypass Lily's protection and thereby enable him to circumvent what the boy has which robbed him of power years ago, when in fact it actually strengthened it.
Many Harry Potter fans have speculated that the Resurrection Stone's power was able to help Harry survive the killing curse and return to living status. Except, that's not how the Resurrection Stone works. While it can "recall loved ones from the grave," the Stone cannot fully restore someone to life.
Harry held the resurrection stone right before he was killed by Voldemort. Even though he dropped the stone at that time he was the Master Of Death. He was in possession of the deathly hallows because the wand was his the cloak was his and then the stone was his. That is why he did not die.
In the books, Pansy Parkinson has a schoolgirl crush on Draco, and they went together to the Yule Ball. However, there was no true love between them. In the Cursed Child, Draco Malfoy's wife is Astoria Greengrass.
Luna married fellow naturalist Rolf Scamander, grandson of Fantastic Beasts and Where to Find Them author Newt Scamander, considerably later in life than Harry, Ron, Hermione, and Ginny, who all married and started families in their early-to-mid twenties.
J.K. Rowling says Draco doesn't have a patronus because he never learned the spell but I think it's because he doesn't have any powerful happy memories to use.
She thought they were only together for the physical side if things. Ginny didn't like her because Fleur treated her like a little girl, not like a respected teenager like Ginny was used to.
In the fourth book, Mrs. Weasley sees Sirius transform from his Animagus form and Ron tells her “it's okay.” Mr. Weasley, Mrs. Weasley, and Sirius are in the Order together in the fifth book, so we can assume that the other Order members know Sirius is innocent.
The prolonged misery of being exposed to dementors kept the prisoners locked within their own minds, so Sirius lost the ability to transform. However, Sirius explained that the knowledge of his innocence kept him sane in a way most of Azkaban's prisoners were not.
Dumbledore's lack of belief that Sirius is innocent is also suspect. Sirius was a member of the Order of the Phoenix which fought against Death Eaters, but Sirius also was as close to James as a brother, the Potters even took him in when he ran away from home.
