Temporary Resident Permit
If you are inadmissible you will not be allowed to enter Canada, unless you provide the right documentation. If you have a legitimate reason to enter Canada that can be justified then you may be issued a Temporary Resident Permit (TRP). A person may be inadmissible for many reasons, which include having criminality, a serious medical condition etc.
At TRP can be applied for from outside Canada or inside Canada. The granting of a TRP is widely discretionary and so every case is processed and decided based on its own merits. You have to make compelling arguments to show the immigration your necessity for being in Canada and that you are highly unlikely to recommit any offense once you enter or stay in Canada.
Extension of Temporary Resident Status
Temporary Residents ( visitors, students, workers) who wish to remain in Canada beyond the eligibility of their Temporary Resident document can apply for an extension of their status, if they meet the conditions and the requirements under the category for which they are applying. Extensions must be submitted to immigration prior to the expiry date and failure to meet this deadline may require the temporary resident to apply for a Restoration of their Status.
Restoration of Temporary Resident Status
Temporary Residents who failed to apply for an extension of their status in Canada generally have 90 days from the date of expire to apply for a restoration of their status. Individuals applying for a restoration must not be eligible for an extension and they must explain why they have lost their status in Canada. They also have to show that they meet the eligibility for the category for which they are restoring their status.