defeat all level 1 opponents 5 times each
No, there is nothing that can do that.
deafeat 3 opponents 5 times in world champion
Duel the higher level opponents more, they give out more experience
Ocean Dragon Lord - Neo-Daedalus comboing with Dimentional Fissure let me say tho the Ocean dragon's effect is a pain to even attempt to activate but if you can activate it and you have DF already activated then your golden! (more or less) XD (as far as i no theres no such card and if there is either konami will make it a pain to use or its ban the card)
Yes, of course. Exactly the same as main phase 1.
After you activate "Heart of the Underdog", you draw a card from your deck like you normally would during your Draw Phase. If that monster you draw happens to be a Normal Monster, you can activate "Heart of the Underdog". You show the Normal Monster to your opponent as proof and draw another card from your deck. If that new card that you draw is a Normal Monster too, you can activate "Heart of the Underdog" again. You repeat the process until you don't draw another Normal Monster.
Walmart or a yugioh store.