5. Are you talking about when on implied status? Or in general without a PR?Some point about this issue:
1-Your SIN will automatically be valid until the end of your implied status (either you hear from your work permit or your PR). You don't need to update it. Explain this to your employer. That should be enough.
2- Your Bank shouldn't need it immediately. So there shouldn't be any problem.
3- Bank generally need SIN for information about your taxes. If you have any saving account, or TFSA, or RRSP account, Bank uses your SIN number to let CRA know of your information, CRA uses these information to decide how much limit you have in your TFSA and if you need to pay any taxes. Also, if you have any saving outside the TFSA, banks issue a T5 tax slip that is based on your SIN number
4- As soon as you receive any result from either your PR or BOWP, renew your SIN number and give it to your employer and your bank. (don't give it to anyone else!)
5- If you don't have PR, you can't get any loan or mortgage.period. Then, why worry about having sin or not.
Hope these helps
Cause I already have a car loan and a pre approval for mortgage without being a PR...