To be eligible for an exchange or credit, your licence will have to be in English or French. If this is not the case, you must provide a written translation of all the information on the licence produced by a qualified translator.
Only if your country has a licence exchange agreement with Ontario: check with your country's authorities to see if this is the case. If your country does not have a licence exchange agreement with Ontario you may still get credit for your foreign driving experience, but you will need to pass all applicable tests.
You can, but you should also obtain an International Driver's Permit from your own country before you arrive in Canada if you are planning to stay for more than three months (you cannot obtain an International Driver's Permit from DriveTest).
No, because of the testing required you can only exchange your licence at a DriveTest Centre.