I am replacing my can light, operated by a switch with a led wafer light in a space without attic access. I have removed the 3 screws from the can fixture and removed it completely. The trouble I am having is removing the frame to the which the can fixture was and the junction box is attached to. The frame is secured to joists and covered again with a small piece of wood. How do I remove that frame? Part 2 - I would like to add another light with its own switch off the above light but I have no other wires other than the ground, black & white. If I use only those wires, won’t my new additional light operate off of the present switch as opposed to it’s own even though I connect another piece of wire from the new light to the new switch? Many thanks!
Given that the old frame is what the junction box is secured to, removing it is not only "probably not needed" it's "probably not allowed, unless replacing the junction box with a different junction box, properly secured."
Just connect the wafer light in the hole left behind, or make a bigger hole if needed to install it. Ignore the old frame, use the junction box.
From this location, you can't install a light with its own switch (unless you like hacky smart-bulb solutions) as this location only has switched hot from the switch controlling this location.