Which RHEL version started to support drop-in directories for particular features?

Issue

To make sure some legacy systems are handled correctly by a configuration management system, it is required to know in which version of RHEL drop-in directories started to be supported for the following features:

1. For sudo, reading configuration from files in the /etc/sudoers.d directory in addition to the common /etc/sudoers file,
2. For resources limits, reading files from the /etc/security/limits.d directory in addition to the /etc/security/limits.conf file,
3. For the sysctl command, reading files from the /etc/sysctl.d directory, in addition to /etc/sysctl.conf.