In the 6th book (Half Blood Prince) Harry told Kreacher and Dobby to follow Draco Malfoy and find out where he is going when he cannot be found on the Marauders Map.
Kreacher obeyed his order.
Dobby the house-elf told Harry about it .
Nobody was a death eater in disguise in Order of the Phoenix. This happened in Harry Potter and the Goblet of Fire when Barty Crouch Jr took polyjuice potion and pretended to be Mad-Eye Moody.
Dobby the house-elf told Harry Potter about it and said it was the perfect place for Harry Potter to teach Defense Against the Dark Arts to the DA group (Dumbledore's Army).
He was told to be in his bedroom where he would stay for the rest of the night in total silence. However, Dobby ruined this plan by deciding he would drop a cake on top of Mrs Mason's head.
Kreacher obeyed his order.
Yes, he does. It was R.A.B(Regulus Acturus Black), who found the locket first. Then he told Kreacher that Kreacher should hide it and destroy it at some time. Unfortunately Mundungus Fletcher stole the locket from Kreacher, and sold it to Dolores Umbridge. Harry, Hermione, and Ron stole the locket from Dolores in the Ministry of Magic.
House elves are bound by strong magic that prevents them from refusing their masters order. In order to prove that Sirius Black's will was valid, Dumbledore summoned Kreacher and asked Harry to give him an order. Harry, trying to think of an order, told Kreacher (who was screaming obscenities) to "shut up!". Kreacher was forced to do so, proving Harry was his master and that the will, which listed Harry as the owner of Grimmnauld, was valid.
Voldemort gave his diary to Lucius Malfoy and told him to keep it safe. Malfoy didn't know what it was and decided to get rid of it, so he hid it inside Ginny Weasley's school books. Harry destroyed it but he didn't know what it was until Dumbledore told him in his sixth year. Voldemort used Kreacher to hid the locket and Kreacher told Regulus what Voldemort made him do. So Regulus figured out what Voldemort was trying to do, stole the locket and told Kreacher to destroy it. Harry and Dumbledore found the fake one and Harry, Ron and Hermione tracked down the real locket. Harry, Ron and Hermione found Hufflepuff's cup in Bellatrix Lestrange's Gringotts vault. Harry figured out that the Diadem was hidden inside Hogwarts. Nagini and Harry weren't ever lost but Dumbledore discovered they were Horcurxes. He also tracked down the ring.
Dobby tried several things to prevent Harry from returning to school. He stopped all of Harry's letters hoping that Harry would think his friends had forgotten him and not return. Then, he turned up at Harry's house and told him not to return. When Harry refused, Dobby ruined the Dursley's dinner party, resulting in Harry being locked in his bedroom. Finally, he prevented Harry (and Ron) from getting on the train, but they flew to Hogwarts.
Dobby the house-elf told Harry about it .
The real necklace was stolen by Sirius brother who gave it to Kreacher and told him to destroy it, however Kreacher failed to do so and instead stored it in the cabinet at Grimnauld Place. In Harry's fifth year they cleared out that cabinet and subsequently through the locket out. Thankfully Kreacher saved it. However after Sirius died Mundungus Fletcher stole things from the house including the locket. Which he then gave to Dolores Umbridge who was going to report him if he didn't.
Nobody was a death eater in disguise in Order of the Phoenix. This happened in Harry Potter and the Goblet of Fire when Barty Crouch Jr took polyjuice potion and pretended to be Mad-Eye Moody.
Dobby the house-elf told Harry Potter about it and said it was the perfect place for Harry Potter to teach Defense Against the Dark Arts to the DA group (Dumbledore's Army).
Yes. They ran a lot of major changes past her and she told them things they couldn't cut (such as Kreacher in the fifth film).
Harry's sock sets him free, he tricks Malfoy into giving it to him; spoiler alert: this piece of clothing becomes Dobby's favourite and thinks that they are suppose to be worn not as a pair but so they don't match each other and he make a pair for Harry latter on in the series ^.^
He was told to be in his bedroom where he would stay for the rest of the night in total silence. However, Dobby ruined this plan by deciding he would drop a cake on top of Mrs Mason's head.