Can the 10 Gigabit SFP+ slots on the Cisco Catalyst 2960-X model support 1 Gigabit SFP modules and 100-Mb SFP modules?
No. The Cisco Catalyst 2960-X models that support 10 Gigabit SFP+ modules cannot support SFP modules that operate at less than 1 Gigabit.
Because an SFP+ slot is compatible with an SFP transceiver. In that case it is acting effectively as an SFP slot. Kind of like an old blade in a 6509 only using half of the backplane fabric, but that's different than the case of an SFP+ 10 Gbps transceiver operating at 1 Gbps.