The GRS-1, when coupled with either a PG-A1 or PG-S1 antenna is capable of L1+L2 GPS & GLONASS.
As for the TopSURV software, do not load a different version of TopSURV without taking a screenshot of the activation codes for the current installed version. Under the guise that the software is no longer supported, Topcon WILL NOT issue activation codes for any version of TopSURV. They consider it obsolete software.
You should be able to load the current version of Magnet Field software, though you would have to purchase at least the GPS+ license in order to activate it.
If the GRS-1 in question does not receive L2 signals, it is likely because it was purchased as a mapping grade unit and is not capable of RTK until the necessary upgrade are purchased. The unit should have Topcon Receiver Utility [TRU] installed on it. If you open that app in “Receiver Managing” mode, you should be able to view the Options Authorization File [OAF] and see what is enabled.