Yes they are allowed in the exam hall. You can carry them along with you. Bit any sort of electronic gadget is not allowed. If you are caught carrying any illegal stuff like mobile phones, calculator, etc then you will be disqualified and strict actions will be taken against you. 

Yes, you can carry. But you cannot mark answer in OMR sheet with pencil. It is not allowed.

You have to fill the bubbles in ORS using a “black / blue ball point pen” only. While pencils can be used to do rough work in the question paper.

For jee Advance guidelines check the below link

https://engineering.careers360.com/articles/jee-advanced-exam-day-guidelines

All the best!

No, the stationary is not allowed in advanced. You will be provided one ball point pen in your exam hall and you need to return back at the end of your exams. You have to do all the rough work in question paper using only the pen provided. Taking other stationary will be marked as malpractice.

BEST OF LUCK !!