Couple of things to make sure before any conclusion:
make sure you ran config wizard on all SharePoint servers after patching.
from add/remove program, Make sure Jan 2019 Kb patches listed there (kb4461605)
also from central admin > upgrade & migration > check product and patch installation status on this page, make sure Jan 2019 KB number is ...
Jan 2019 CU should include all the fixes from the Dec 2018 CU. You only need to install the Jan 2019 CU to patch it fully. Please dont forget to run the PSConfig wizard at the end on each server.
January 2019 CU for SharePoint 2013 product family is available for download
I dont think you can uninstall it. In this situation, i would complete the patching process. Run the config wizard on all server and complete the patch.
I would also do the same on the lower environment as well because your prod is now (may be) higher build number.
Farm build number will increase only if you will run SharePoint Configuration Wizard after SharePoint cumulative updates(or service pack) installation.
You do not need to run SharePoint Configuration Wizard after installation Windows server updates.
If you will plan to install .Net security patches - be careful with this. It may affect Workflow ...
First of all let me point you to this blog https://blogs.technet.microsoft.com/stefan_gossner/
(on the right hand side you will get a lot of usefull resources re. patching process for SP)
Yes it is possible if your windows update is set to update as well other Microsoft product. In that case patches for SP may be delivered along with OS patches.
SharePoint always patched by CU, their is no separate patches unless MSFT announced it. but their couple of independent product which can be patched independently.
Workflow Manager Server
Office Online Server
Distributed Cache (App Fabric) should be patched independently of SharePoint.
if you apply the SharePoint Server 2010 September 2019 CU, it will cover all the security fix (CVE-2019-1257,CVE-2019-1260, CVE-2019-1295).
You have SharePoint server then it is advisable to install the server cu which include the foundation cu as well.
This is normal behavior in SharePoint 2013. Not all CUs include database schema changes and even if they include them the version number for these schema changes might be slightly smaller than the highest build number included in the patch.
Do not trust the version number that is shown in the Manage Servers section. Instead head over to the Upgrade and ...
The Configuration database version 15.0.15131.100 only indicate the version of configuration database. If you goto CA -> Application Management -> Manage content database, and click into each content DB, you will find each of them have a schema version too.
You can check your upgrade status by CA -> Upgrade and Migration -> Check product and patch ...
Your only requirement to putting the latest patch is to have SP1 installed. As you are on Oct 2017 CU your are already there. So there is no need to install the any patch in between. But I would advise to install them more often (on monthly basis if your farm is exposed to internet) it will reduce the time required for the content DB updates and general ...
Updates are displayed here: https://docs.microsoft.com/de-de/officeupdates/sharepoint-updates
The currently latest CU is KB 4464514 - April 2019
The problem you mentioned was not due to a SharePoint update but rather .net-Framework.
It is recommended to always be on the CU which is 1 month prior to the current month.
That way you are on the most stable CU and aware of any issues or exceptions occurring due to the current month CU .
I have recently patched my SharePoint 2013 environment with the April 2019 patch and it looks the most stable patch right now .
Following is the ...
If the windows update does not contains the SharePoint updates then no need to run the Configuration wizard.
their is no harm to run it if you want, but keep in mind it will cause an outage on the server where it is running so plan it.
I have done a test in my SharePoint 2013, patched on SharePoint servers with Jan 2019 CU on SP 2013 Servers. After patching, the SharePoint build number is equivalent to Dec 2018 CU instead of Jan 2019 CU.
It is a normal behavior.
Run SharePoint 2013 products configuration wizard in all SharePoint servers.
Or you can run the following PowerShell on all SharePoint servers:
PSConfig.exe -cmd upgrade -inplace b2b -wait -force -cmd applicationcontent -install -cmd installfeatures -cmd secureresources
You don't need to backup the farm before running this command.
Oh, Your build number refers to the SharePoint Server 2016 Release Candidate that not supported to be upgraded to RTM!
Note: In some rare cases, you may installed RTM but it shows the RC build number! it's a bug! and in this case, there is no issue to install the latest CU update.
So if you are sure you already installed the RTM version but it shows RC ...