Ok. I may have not phrased my question accurately. 

This past Sunday August 16th we had a class and our teacher decided to send out the link actually Wednesday the 19th but there was no option to create one. Is there a time limit on creating links after the lesson has been taught? I am aware the generated link only lasts a week.

Is the only option to generate these links available prior to the lesson and not after?

Hopefully this is more clear . Thank you for your time.