At this age subjective testing is not possible hence accurate number can't be given and with the help of retinoscopy an approximate number is given which may come out 2to3 be lower or little higher. Hence don't worry get an approximate number like --- 2 dispensed if axis in both prescriptions is same Or Have a third opinion.

Hello A. Yes.  You must consult local paediatric ophthalmologist for third opinion B. That eyedrop is not harmful

You have to get the eyes checked by putting a drop which will blur the vision for atleast 24/36 hours. Then a correct number will be determined... not at all harmful

Yes, You should consult again to verify the number. And eye drops used to test power, if repeated with a gap , are usually not harmful unless the patient is allergic to it.