I’ve been following a tutorial in Blender 2.82 (the tut is in the same version) and I got to a point where I need to merge vertices ‘at Last’. The menu in the tutorial has both ‘at First’ and ‘at Last’ but the same menu on my machine has neither. I only have ‘at Centre’, ‘at Cursor’, ‘Collapse’ and ‘By Distance’.
It probably won’t make much of a difference but I don’t like not knowing why mine’s different from the one in the tutorial. Is there something I need to set, or reset, to get all the options? Or is there something wrong with my version?
Just to expand on @WombleMonster 's answer.
To get the option you must individually click on a set or group of vertices. If you use a box, circle, or lasso select it will not work…An order doesn’t really matter, hence merge First, Last, or at Center options.
To pull up the options, use either the top bar, Right Click, or Alt+M.
I actually thought I’d selected them correctly but I’d used the box selection tool to drag-select the first then held down shift and did the same for the second. It worked once I’d actually click-selected each.
IMO this is a serious and repeating design flaw in Blender: rather than disabling controls by ‘ghosting’ them, they remove them entirely from the interface. This interferes with discoverability.
If the FIRST/LAST options were in the dialog but ghosted, at least users would know they were in the correct place, but that something was wrong. This is a clue that the selection modality was incorrect. A line in the status bar wouldn’t go amiss either.