no your not allowed to have anything in your hands, it's just to read, skim over the paper to see the layout and figure out what you will attempt first.
In seriousness, i did my multiple choice section and used calculators during my reading time and never got caught. If you are smart about it and have complacent supervisors it is possible. But i couldn't really recommend it
During reading time, you must not write, use any equipment including highlighters, or annotate your examination paper in any way. For examinations in which dictionaries are permitted, you may consult, but not annotate, your dictionary during reading time.
Yeah calculators can't be used during your reading time. Depends on the subject but usually you can focus on the multiple choice section first and use like your finger nail next to the answer or structure an extended response for a section later on in the paper, it doesn't really matter as long as you're using your time well.