How can one perform ghusl after menstruation when there has been a liposuction procedure on the back and abdomen, with a medical corset that cannot be removed or exposed to water due to pain, and on it are impurities of blood and feces that are difficult to remove completely?

As for the obligatory ghusl (definition) to purify from menstruation, if it is possible to wash some limbs without harm, then they must be washed, and tayammum (definition) performed for the remaining parts that cannot be washed. If it is not possible to wash anything, then tayammum suffices.

As for impurity on the body, no more is required than what can be purified. What the questioner is unable to do— "Allah does not burden a soul beyond its capacity." The condition of removing impurity for prayer applies when there is knowledge and ability.