If SB street rave is in hollow bastion, uncle scrooge does it. If it's the one in twilight town, the mail lady has it, she's standing by the grandstander ball at station hights.
Poster duty requires the glide and arial dodge abilities, as well as some mad skill. Everyone I've seen, including myself did it in 29.8 seconds.
Some of the requirements for tournaments include a high enough level, maxed out form and summon levels, completing the point requirement in the previous cup, and being far enough in the story. I dunno the details of the first 4 tournaments, but I would think the cerb cup should just happen after a certain point in time. Like the coliseaum will say "A new episode has been added."