Yes-you can apply to a mounted baseplate by twisting into it or install the whole assembly
The Everbilt Satin Nickel Spring Door Stop is 3 inches long.
This Chrome Spring Door Stops are not currently available in a 5 pack.
No. They are "brass finish". Checked with magnet - spring steel underneath.
Yes, there are bigger packages the contain more than just one. I only needed a few so I purchased them individually
There are a few options in stock at store #622 - part numbers 13531, 14515, or 15727. Links provided below. https://www.homedepot.com/p/Everbilt-Oil-Rubbed-Bronze-Kick-Down-Door-Stop-13531/202950148 https://www.homedepot.com/p/Everbilt-Oil-Rubbed-Bronze-Step-Release-Kick-Down-Door-Stop-14515/206743153 https://www.homedepot.com/p/Everbilt-Oil-Rubbed-Bronze-Commercial-Grade-Kick-Down-Doorstop-15727/202034257
This is 4"
This stop measures 3" long.
The spring itself should unscrew from its base. Thus giving you access to the screw. You may want to watch the installation video on this web page.