Lets Play Yu-Gi-Oh! The Duelist Of The Roses Part 8 The End and New Beginig 

Well it’s canon, the final boss, strongest duelist of the era was beaten by someone who had freaking mushroom man in his deck.

You could have fused dragon zombie with a plant like the monster with 350 attack and 300 defense at 25:57 to get pumpking and power up zombie monsters!

you can attack the deck leader with any monster no matter the attack while they are on the crush space. your monster will not be destroyed. the monster is only destroyed when you advance to the spot.

Afaik, you can reincarnate after either winning or losing five times in a row. Btw, the qualities of cards you get depends on the Deck Cost of the card you exchange for them. If you have any cards that cost 50+ that you don't need, those give some very high return. Or anything higher.