Hi Mehar, you should have applied for the childs TRV with your application otherwise they'll review your child's application separately. Submit the TRV application for your child with the letter of explanation and I hope they'll get the visa soon! Don't apply for study permit as you'll need to submit the supporting documents from the educational institute to get that visa. Children can study on TRV until high school if parents have a work permit. If you want your child to accompany you in Canada you should have send the updated imm0008 and adding all your dependents info in their by selecting the option they'll accompany you in Canada. Hope it helps.