Incorrect section in tds return

1. Challan correction can be done online. 

A few clarification on this...

1. When do we make a request for correction (available under defaults) and when do we download conso file.

2. What would be the type of correction - C1/C2/C3....

3. After downloading Conso file, do we prepare return in normal course and file it online.

Thanks

Can someone pls revert on this..

Can we upload the rectified return online or is it compulsory to submit the signed copy at TIN centre.