Trouble with Edit Mode

So I’ve been learning blender via the tutorials on the and the one I’ve been doing the underground subway tutorial. So i saved the project last night, but when i opened my project this morning when i went into edit mode I could only select vertices on 1 object at a time, I know you can select more then one object into edit mode because I did it yesterday. I’m new to blender so it could be something simple but i need help.

U must understand basic concepts of referenced objects which spans over beyond Blender almost in every CAD program …selecting vertices of just one object is possible at a time. But when u have duplicated objects in the scene (Alt+D instead of Shift+D) u select one and all instances are selected as well. They share the same mesh so it is obvious that they get selected as well. Try to experiment with this.

Yeah I had already had the circle duplicated and i wanted to select all the (6) circles and tab into edit mode and extrude them to make wires but i can only have 1 circle in edit mode at once for whatever reason even thought yesterday I could select more then once object into edit mode even if they were two different objects not just one copied

In object mode select all your objects and Menu > Object > Join (or Ctrl+J). Now they are separate meshes in the same object. (Actually, they are loose mesh parts all belonging to the same mesh data).

While in edit mode select all and Menu > Mesh > Vertices > Separate (or Key P) > By Loose Parts -and they will all be separate objects / separate meshes again. You can also separate by selected vertices or by materials this way.

Delete all but one object and Alt-D if you want exact copies (which will all edit at the same time if you select/edit one of them). Multiple objects sharing the same mesh.

Or shift select all your objects and Menu > Object > Make Links (or Ctrl-L) > Object Data -and all of them will turn into a copy of the active one (the last one you selected). Again, multiple objects sharing the same mesh.

Shift-D duplicates object and mesh.
Alt-D duplicates object but the duplicated object shares the same mesh data. Select/edit one and the other gets edited as well.

As mentioned above, experiment… but look in the outliner at the objects and the data names inside them for a clear picture of what’s going on.