For compare and merge the best way is to compare your 2013 R2 custom report with 2013 R2 standard Cronus report (from the same CU if any) using a text editor like compare it.
When you compare those two reports you will identify the customization which you can merge.
But still, if you want to do it the way you plan -
1. You need to uninstall the report Viewer for 2016.
2. You need to install report viewer of 2013 R2.
3. then Re-install the Report viewer of 2016. ( I am not sure will it overwrite but i tired with 2013 and it used to work).
** Report Viewer can be found in pre-requisite folder of the product DVD.
Agree with what Saurav suggested, or take 2013R2 version and 2013R2 cronus version as text files and use a text comparison tool to identify the differences. Then incorporate those changes in to 2016 manually.
Software Developer,
Archerpoint India Pvt. Ltd,Chennai.
Answers
When you compare those two reports you will identify the customization which you can merge.
But still, if you want to do it the way you plan -
1. You need to uninstall the report Viewer for 2016.
2. You need to install report viewer of 2013 R2.
3. then Re-install the Report viewer of 2016. ( I am not sure will it overwrite but i tired with 2013 and it used to work).
** Report Viewer can be found in pre-requisite folder of the product DVD.
Thanks & Regards,
Saurav Dhyani
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Archerpoint India Pvt. Ltd,Chennai.