Sheetmetal part intersects itself ater bend operations,etc.

For the sheetmetal gurus out there.

1. The error - part intersects itself ater bend operations why? Is there a way by which I can find the intersection as in Interference Detection in Assembly Mode? I can not see visible interferences and bend radii are all within limits.

2. I can not create a Flange on the Bottom Flange after editing the profile to cover the complete opening.

3. Can I  create a flange with a closed corner next to an existing flange, without using the close corners feature afterwards?

SolidworksSheet Metal