Multiple outputs for "apt-cache policy <package name>"
"Candidate" indicates the version that will be installed.
It's always the highest version if different ones are available from different repositories. In the specific case of your question it comes from the "focal-updates/main" repository that you manually enabled. Disable it if you want to current version instead of the backport.
Choose between the two versions:
1:2.25.1-1ubuntu3.2
1:2.25.1-1ubuntu3
Version x3.2 is higher than x3, so 1:2.25.1-1ubuntu3.2
will be installed...unless something on your system requires version x3.
Choose between different pockets that offer the same version:
500 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
Ha -- it's a trick question: The repositories are structured so that all packages sit in one directory (/pool). Both lines point to the same package in the pool.