She fell hard. From pop princess to tabloid terror. The crash and burn appeared to have left permanent damage. Who could rise from such a ruined reputation? But when Britney Spears’ first arena tour in five years arrives Sunday in Tampa, people will be flocking to the St. Pete Times Forum to celebrate a momentous comeback. Spears is touring in support of her new, well-received, highly personal, chart-topping album “Circus.” The sexy again singer’s biopic-worthy re-emergence is something few could have foreseen a few years back. Remember when Spears sported no underpants, a shaved head and a look of utter craziness? Here is our time line of key events that brought Brit-Brit to the depths of celebrity purgatory — and then back on top again.