We have application developed in "Milestone XProtect Corporate 2019 R1" SDK, will it work with "Milestone XProtect Corporate 2019 R2" VMS Products(NVR)? without changing code with R2 SDK.Please let us know.

Yes! - https://developer.milestonesys.com/s/article/about-MIP-SDK-compatibility-with-XProtect-product-versions

Thank You Andersen.