1) if you have the server backed up and have ability to rollback the patch you should be fine to apply OS patches.

2) The version of RapidStack installed may rely on Java 7 or Java 8 and Linux, UNIX, or Windows Server 2012/R2 compatibility.

More details are available here.  https://www.java.com/en/download/help/sysreq.xml

Any patch coming out of Microsoft ,REDhat, Sun, etc will not go through regression testing unless there is a specific request as not every patch available for OS, Java, database , etc  is applied to every environment.  

Please note that TLS 1.1 and 1.2 are only supported on the 4.2 version of RapidStack, BusinessObjects.  You may not be using TLS currently but if it does come up it will need to be part of an overall upgrade strategy as we have several customers upgrade for TLS and other security and performance improvements to 4.2 Sp4.