Upgrading from (RINEX: 3.02, ReachView: v0.4.9, Reach image: v1.2)

I am trying to upgrade from (RINEX version: 3.02, ReachView version: v0.4.9, Reach image version: v1.2) to the latest firmware.

Do I follow the instructions listed on this page?

https://docs.emlid.com/reach/common/reachview/firmware-reflashing/

Yep.

I would pick the Terminal Guide over the GUI Guide myself.