Instagram pictures were cropped when I didn't ask for it.

Hello,

For Instagram, I took pictures of my father's picture album, made in the 1930's. The pictures looked good on my PC, framed well, but when they appeared on Instagram, part of each one was not shown. They were not as long as the pictures.

I skipped the cropping step because I wanted to show the whole thing, but it's like it cropped it anyhow. Could I have avoided this by using the Cropping ratios I saw when I clicked on some icon? Or is there some other way out of this? Or must I reshoot the pictures, leaving a border that instagram can then crop away?

If cropping will fix it, can I crop the photos that are already there, or do I have to do it when first uploading?