Apologies for the confusion on the pin-names, we tried to keep one footprint/schematic-block for several modules (e.g. SARA-G350, SARA-U270, SARA-N211, SARA-R410, SARA-R412). But as you might've noticed, this gets confusing quite quick (maybe even more when everything is called RSVD). I'll discuss this with my colleagues and see if we can make this a bit more clear (in future revisions).
As for pin 2, this is used on the 2G/3G-modules (e.g. SARA-G3, SARA-U2). This is V_BCKP and is typically used as Real Time Clock supply input/output (you can check more here: https://www.u-blox.com/sites/default/files/SARA-G3_DataSheet_%28UBX-13000993%29.pdf, page 18/19).
Hope this clarifies it a bit!