I don't think that you have to replace the disposal. I would think that if you were to compare the threads on this strainer bottom and a sinkerator bottom and see if they match. Then you know what will work or not. I don't have a disposer with mine, so I can't tell you positively. John
You don't need plumbers putty. Use a clear silicone for kitchen and bath.
I have not had any issue with my drain ( same one as in the picture / your description). I have had it for about a year now and it looks almost like new. I rinse the sink out after each use, but I do not wipe it down and have never used anything but dish soap on the sink or drain.
Yes, turned a gray color the very first day. NEVER used any harsh chemicals.
Yes but get a different one that is all metal
Yes it should fit any sink with a standard drain opening.
Yes but since the part that connects to the pipe is made of plastic, it is very difficult to intall it. Once, it was installed the plastic cracked and was leaking. Purchase one where the entire strainer is metal.
This drain has an end that will fit a 1 1/2 inch drain line.