Can you turn a mono recording into stereo?
If you want to add stereo effects to a mono recording, duplicate the mono track, (Press"Ctrl"+"D"), then join them to make a stereo-pair, (which is actually called "dual mono" because the L&R tracks are identical). Then apply stereo effects to the dual-mono track to stereoize it, e.g. pseudo-stereo , chorus, spin.
Can you convert dual mono to stereo?
…if you select both mono tracks at the same time (ctrl+click) in a multitrack session, you can right click and go down to “bounce to new track >selected clips only” and it'll create a new stereo track using those two monos.