Going into ruku' thinking that the Imaam made takbeer

Q: While praying Salaah in Jamat (congregation) a person was standing far from the Imam and also there were no speakers. At one point the person thought that Imam Saheb said Allahu Akbar, and so he was going to ruku. As he was doing so he found that the rest of the muqtatis were still standing (the person in concern heard it wrong) so he again stood up. Now my question is that is the Salaah of the person, in concern, valid or should he repeat his Salaah?

Certain things I heard when attending Hajj classes

Q: I recently heard from a Moulana whose name I will not mention and he does Hajj classes that when you are flying to Mecca for Hajj then:

  1. In the Plane you can sit in your seat a read your namaaz as you are flying North and facing Qibla! Can this be done?
  2. When making wudhu in the plane you can make massah over your woollen socks! Can this be done?
  3. If you make wudhu in your room and then go to the Harem and you then break wind or go toilet your wudhu does not break due to the massive amounts of people in the Harem and it would be highly inconvenient to go and try to make wudhu again in the Harem! Is this a correct statement?