cillyx5 said:
Is there a grace period for them accepting older versions of forms?
...and how do I know which version/date of the form I have? I don't see it written on the form anywhere.
There isn't much grace period, CIC has sent back applications if the form was even a day out... in some cases even if the form was updated a few days after it was mailed. It's completely up to the visa officer's discretion if they send back your entire app, or just ask you to redo and resend that 1 form.
Look at the bottom left corner of the form. You'll see a date code i.e. (08-2014) means your form was updated Aug-2014. Always do a final check against the CIC website, just before you mail everything.