Red Hat Linux was a distribution developed by Red Hat until 2004. The first version of the distribution was released on November 3, 1993, and the operating system was originally called Red Hat Commercial Linux.
It was the first distribution to utilize the RPM package manager, and it formed the basis for many derivative distributions including Mandriva Linux and Yellow Dog Linux.
In 2003, Red Hat discontinued development of Red Hat Linux and focused on Red Hat Enterprise Linux (RHEL) which is aimed at supporting enterprise and commercial applications. 
Fedora, developed by the Fedora Project community with support from Red Hat, is a free version suitable for personal use. Official support for Red Hat Linux 9, the latest version of the system, ended on April 30, 2004.
Today, the RHEL developer announced the new beta version of the Red Hat Enterprise Linux 7.x series.
The new development release, Red Hat Enterprise Linux 7.4 Beta, includes bug fixes and some new features for the 7.x product line.
“To help protect against the latest threats and provide a more secure platform for mission-critical applications, Red Hat Enterprise Linux 7.4 Beta introduces several new security features, including:
- Support for NetworkBound Disk, a tool designed to reduce the administrative scale of disk encryption.
- Improvements to OpenSSL HTTP/2.0, enabling the use of several new TLS (Transport Layer Security) security protocols in OpenSSL, and Application-Layer Protocol Negotiation (ALPN).
- Updated audit capabilities, designed to make it easier for administrators to filter events recorded by the audit system, gather more information from critical events, and interpret large numbers of records.”
More information can be found in the official release announcement and release notes. Downloads are only available through the Red Hat customer portal.
As for the rest, be patient until CentOS releases the corresponding beta version.
With information from Wikipedia.
