Hi Rohit !

Most of the seats in AU and JNTUK are filled  by GATE  students so the seats left for PGCET students are very less .

The students applying through PGCET needs rank under 100 to get admission there but your rank is much more than that , so you have very less or no chance of getting a seat there.

And as far as changing your background is concerned , you can only change your background while filling the form. After you have got your rank ,you cannot change your branch or  background . For more details about it ,follow the given link :

https://engineering.careers360.com/articles/ap-pgecet