form 1294 study permit outside Canada provide the opportunity to declare other variations, it asks have you used other names, mention your spelling variations there, also include an affidavit, which is not big deal you can make from a notary public in nominal charges. but stick to passport spellings in all you official documents, in your university applications, in your Canadian ids etc, passport name is the basic thing other variations can be explained, Ahmed is Urdu name and it is written in two ways this is well known to every one.