Is it too late to study physics?

Definitely not too late! I've known graduate students in physics entering anywhere between 20 and 30, and I know there are even older and younger out there. Even better, it's not like information technology is a completely irrelevant- in physics (particularly high energy physics) we routinely deal with big data and I'm sure you could apply some of what you learned there.

If you've kept up in physics and mathematics, that's a good thing as well. As far as entrance examinations go, I would recommend looking up what textbooks your university of choice assigns their undergraduate physics majors, and think about studying that.

The difference between the M.S. and Ph.D. varies a little bit, but generally the M.S. is a short program mainly based on coursework (though there may be a thesis as well) and the Ph.D. is a much longer program that universally requires a lengthy dissertation.

If I compare your case (which is similar to mine) I will graduate when I'm 27 and then I can start a phd so i will be 31 years young :) If you love what you do, just do it ! eventually it will be worth it !

I begun a Computer science degree at 24, and at the end of the first year I decided that I really liked studying Physics far more than IT. I wanted to switch to a physics degree but I wasn't qualified enough and had to do a year long science foundation program first. Undeterred, I took the course and 5 Years later I had an MSC in Physics. Last year (after a year working), I begun a PhD in theoretical physics - I am 31.

It's not too late :)

Good luck.