From the FCOM (abridged)
Speedbrake control (lever):
Spoilers 2,3,4
Inhibited:
Flaps in Config Full etc.
For maintenance purposes lever will extend # 1 surfaces when stopped on ground whatever slat/flap config.
Ground spoiler control: Spoilers 1,5
Armed with speedbrake lever (pulled up to armed position)
Auto extension when both MLG touched down when Ground spoiler armed and all T/L at or near idle or reverse selected on at least 1 engine (other T/L at or near idle) if ground spoilers not armed.
Ground spoilers retract:
when ground spoilers disarmed etc.
Based on that information: Spoilers 2,3,4 can be extended after touchdown using the lever if in config. 3 but not Full
Ground spoilers cannot be extended manually by moving the lever rearward after touchdown. They are only automatically extended and retracted when a series of electrical continuity conditions is met; one of them being the switch activated by pulling the lever up to the armed position. Moving the lever rearward has no effect other than during the maintenance function described above.