1) I was hired for the higher post and made into an Engineer upon joining. The reason HR gave me was very lame. They said that company policies have been changed there is nothing that they can do about this and if you want to accept then serve otherwise leave. They have done the same thing to many people in the company.
2) The notice period is 3 months and you cannot buy off. Yes, you need to serve complete 3 months notice period. This is another mind-blowing strategy they are using to retain their employees without giving them a hike.
3) HR lies about policies in interviews. Half of the things they tell are fake which are realised only after joining the company.