Yes, you can do the reset from the button or - if you have access to the unit (like you have) from terminal command line or winbox (easier).
See configuration reset here:
https://help.mikrotik.com/docs/display/ ... Management
https://help.mikrotik.com/docs/display/ ... ationReset
The first "symptom" that the new configuration is the right one is that - again in theory - since you have a sticker, the new login will be "admin" and the password the one on the sticker.
Of course there is a risk involved in this procedure, possibilities are:
1) the device is the "right" one (i.e. it has not been exchanged) and the password on the sticker will work (good)
2) the device, no matter if the "right" or an exchanged one has anyway a factory configuration with blank password.(good)
3) the device is definitely an exchanged one, the password is required and the password on the sticker won't work (bad). In this case it is still possible to do a netinstall to recover the unit, but it is a more complex procedure.
Checking the serial numbers of the two devices you have may give a hint (I presume that Cube pairs have consecutive serial numbers, but I may well be completely wrong).
Also the mac addresses in /interface bridge could be sequential.
In any case, before any attempt, you should follow the instructions here:
viewtopic.php?t=203686#p1051720
and export the current configuration of both devices, saving them on your PC.
The files are plain text and the needed info (minus the router password) are in clear text, not obfuscated/encrypted).
The data that changes between sets of pairs (but that you can also change yourself) should be:
password <- /interface w60g
ssid <- /interface wireless, /interface w60g
wpa2-pre-shared-key <-/interface wireless security-profiles
And likely also mac-address and remote-address (in the /interface w60g station settings) but these should be "local" MAC's that can be generated manually.
Once these are set correctly, you just connect one of the two devices to a PC, point it in the general direction of the other, placed a few meters away, connect this latter one to another PC and you should be able to see how the data passes from one PC to the other, if everything works correctly a pair of Cube Pros should work exactly as a "dumb" two ports network switch, i.e. connect transparently the devices connected to them (hence the name as "wireless wire").
To change the settings, depending if it is just a few settings/values or entire snippets of configuration you could use Winbox GUI or a terminal window (still open from within Winbox) using command lines (but copy/paste is possible, so it is not particularly difficult)