With a tub strainer dumbell wrench.
scrape it with a razor blade...assuming the tile is untextured porcelain
Yes, the whirpool duet tubs are made of porcelain.
Porcelain is a type of ceramic; it is not part of a steel tub. If the tub were made of porcelain it would not be made of steel. Enamel is a kind of tough paint that can be used on steel, or on porcelain.
softscrub
Possibly, if you really cleaned the tub aggressively with lacquer thinner or similar de-greaser.
A good basic cleaner is baking soda made into a paste. Scrub the stain with the paste then rinse. Spraying with vinegar before rinsing can help lift extra dirt from the surface. Do not use ammonia, it can damage the finish. [I found this out when I mixed ammonia and soap to remove a copper stain on a tub]
it is a metal tub used for washing.
Once the old tub gets into the drain it is impossible to remove.........
By disconnecting the tub shoe from the waste tee and removing tles around the tub
By un surrounding it
Pop them. Tediously. One. By. One.