Unable to Set Edge to Edge Header and Footer

Hi

Objective: When we convert the excel to PDF or print - the design should be edge to edge of the page.

While setting the header footer with an image - that sizes itself to 210mm in width for an A4 page setup with margins all set at ZERO - am still unable to set the same for PDF or print. Please find attached images for your reference. The first shows the conversion issue, the second a screenshot of the setting.

Besides this, tried the background setting possibility - with a background image of the size 297mm x 210mm in an A4 page, however, the image when set as background, appears to be extremely large and entering other non-selected pages. Image below

And then I tried inserting the same through shapes, which helps me get close to what is intended, however, unable to do MOVE TO BACK / BACKPAGE - to be able to fill the excel columns and rows. Image below

Can anyone please assist?