Rak2245 - Change freq to 868mhz

Is possible to change the factory freq? It comes in 915mhz but I need the board in 868mhz
it´ve some resistors.

Those resistors are just markers that can be installed by the pick and place machine at the same time it installs the components surrounding the radio that make it actually suitable for a given band. The configuration that makes it build an 868 MHz module includes the indication resistor in one place, the one that makes it build a 915 includes on in another place, etc.

Changing the visible resistor would have no effect beyond creating confusion.