No. There were plans for a Sinister Six movie but when The Amazing Spider-Man franchise was cancelled after the second film, the Sinister Six movie was cancelled as well.
Yes
Yes
Websites have announced that a spin-off for the Sinister Six is currently being planned for future release. It will be set in the same universe as "The Amazing Spider-Man".
The Sinister Six will have their own spin-off.
Sometime when they have decided all villains who will be used in the teamup have made their appearances in the rebooted Spider-Man series.
There's speculation the Tom Holland Spider-Man era might introduce Sinister Six but nothing has been confirmed.
Sony plans to feature a teamup of several villains in a spin-off- but Spider-Man himself will have to be included so they can have somebody to fight with.
NOPE
Ultimate Spider-Man - 2012 Sinister Six 2-6 was released on: USA: 17 February 2013 (Release of official version)
It's not! It's more atrocious then scary!
No one is the Sinister Six in The Amazing Spider-Man 3 because TAS-M3 does not nor will it ever exist. The Amazing Spider-Man film franchise ended after two movies.
Ultimate Spider-Man - 2012 Return of the Sinister Six 2-25 was released on: USA: 3 November 2013 (video premiere)