According to the manufacturer (minidso.com), hw 2.82 is just small layout difference from 2.81. You can use same software on both.
You are correct, APP 1.13 and SYS 1.64 are the latest stock software.
However there is newer DFU 3.46C with Mac support. Here is complete hex with DFU 3.46C, SYS 1.64, APP 1.13, FPGA 2.60 https://www98.zippyshare.com/v/i5QYCNXj/file.html
I also recommend to check out this custom firmware Wildcat 6.5 for hw 2.8x. https://github.com/MotoMaxis/DS203-DSOQuad He has made special FPGA to make DS203 more powerful.
As to why your 2.82 now shows as 2.81, I think part of memory in STM32 that has the HW version got changed somehow. You will need to search your dump for 322E3831 to find it. But its really a cosmetic issue with no effect on operation.