Processing time for Visitor visa from Delhi

Hi all
as per Canadian embassy website, the processing time for visitor visa from new delhi should take less than 1 month.

1. can anyone confirm from experience what actual processing time (from application to final visa) is likely to be ?

2. Also is it required to visit Delhi in person to obtain visa ? The visa is for parents who are 60 yrs. What if medical exam is requested ?

3. If the parents already have valid US visa (and have travelled before to US & returned to India last year), does it improve chances of getting canadian visa ?

4. For how long is the Visitor visa valid ? I am confused if it is 6 months or 1 year ?

Any replies would be greatly appreciated..

Thanks
TVV