1) 'G' clamps used to hold emergency fishplates to the rail until a proper repair can be made.
2) don't know - possibly for holding van doors open?
3) Top left - metal key for holding bullhead track in chair. Are the rail sections metallic? If they are plastic/fibre, then they are insulators that fit between the ends of rails to separate two different track circuit sections. The spike between the two rail sections is used to hold down flat-bottom track, usually with the rail resting on a baseplate - the spike passes through a hole in the baseplate into the sleeper to hold both track and baseplate down. Three or four spikes would be used for each baseplate.
4) Fishplate - can't see if it has any special features.
5) Clamp to hold a point blade firmly in place when a trailing point, not normally used for facing movements for passenger traffic, is to be used for such. Once clamped in place, the loop is swung up and holds the handle, which is then padlocked to prevent movement of the clamp until the train has passed; also prevents unauthorised removal of the clamp.