all companies nowadays apply salary banding, which overlaps where one grade's lowest salary will certainly be lower than the highest salary of the grade below, and so on. I've not worked in QP, so I cannot comment whether the band you said is true or not. However, if you were granted the highest level salary for the grade, just beware that next year you would not get an "actual" salary increment unless you move up a grade (which can be very, very difficult to accomplish). you would be getting somekind of compensation in lieu, calculated annually based on what you would have received, but it is still worse than getting the actual increment.
As for the onsite interview, I can't help you much. Hopefully others, more experienced ones, would share with you.
Good luck.