My 8 Year Old Rabbit Has Poo Stuck To Bum, Hair Loss And Flaky Skin.what Do It Happen?

Depends what kind of poo, if its loose its not good if its pellets than its ok.
Loose feces is an indication of an improper diet, give it timothy pellets and timothy hay, fresh vegetables. Give fruit only as a treat but for now hold it all together. As for flaky skin take your rabbit to a vet it is most likely a mite infection and is easily treatable ( you can not see these mites with the naked eye )

For the poo part just shave the hair around it's behind.
For the OTHER part try taking him/her to the vet this doesn't sound normal!