Carpet install questions

Firstly, merry Xmas and a happy new year to everyone here.
I’m about to install a new carpet set into my 67 barracuda fastback. On the rear of the flip up seat, as well as along the top of the rear flip down plywood trunk divider, the old carpet has some slot screws with washers helping to hold the carpet on.
I’m assuming that these were not there originally and was an attempt by the previous owner years ago to hold up the edge of the carpet where it started to fail from the plywood.
I’ll attach a photo, but I wanted to confirm that these screws are not factory?

And my second question is, what type of adhesive should a guy use to glue the new carpet to the plywood on the back of the fold down rear seat plywood, and the fold down divider?

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