Why can I see through the objects in Solid mode ?? isn't it what x-ray mode is for? I don't know why its happening but its making me crazy.....
Tried changing the clip start and clip end, tried tweaking some values in viewport display under Object Property tab, tried to find out where the hell this Limit selection to visible is (sadly not available in blender 2.9+).
Does someone knows how to solve this issue ?????
Edit Mode - Side view screenshot for better understanding how the overall mesh really looks:- 
Edit Mode - Front view with solid mode ON but X-ray mode OFF, chair's Back Leg visible through the mesh :-  
Same as previous image with X-ray mode ON :-
Looks like you have enabled Viewport Display &gt; In Front in the Object Settings of the chair object.