The printer cannot do automatic duplex scanning (only the GX7050 can do that), but it does have manual duplex scanning. Both for copying and scanning. First the whole stack is scanned on the front side, and then you have to manually reload the stack according to the animation on the screen so that the back sides can be scanned. The printer then puts the scanned pages together in the correct order.

Certainly sufficient for occasional double-sided scanning of documents with a few pages. Too tedious for regular use, and if the documents are too long, the memory will probably run out at some point.

WARNING: The GX6050 is NOT capable of DADF (automatic scanning/copying of DOUBLE SIDED originals). Only the more expensive GX7050 can do this!

The GX7050 is indeed capable of double-sided scanning and OCR.
I've just installed it to my satisfaction as a replacement for a Laser MFP.

The 7050 has duplex scanning, the 6050 does not (you just have to be patient until the scan (as well as the print) starts at some point (see evaluation)).

No, the GX6050 does not have duplex scanning. Only the bigger brother GX7050 has that.

yes, duplex scan available.