Lots of questions! Prolapsed rectum, or procidentia, is when the rectum turns inside out, like a sleeve, and protrudes through the anal opening. Common causes: constipation, pelvic floor dysfunction. Not "reversible" in adults; may be in kids. Treated with surgery if symptoms warrant or complications occur. Four questions, four answers!
Bottom falls out. Prolapsed rectum is not hemorrhoids. It is falling of the rectum varying amounts up to, and including, falling completely outside the anus. It is due to lack of pelvic support internally; can be seen with certain parasites (whipworm), chronic psych meds, chronic constipation, birth trauma. Other. Usually needs surgery to "tack it in place". Generally, excellent response to rx.