Here are the items and powerups in the game
Items
Coin: The most common item in the game, get 100 for an extra life.
Red Coin: Collect 8 Red Coins when you pass a red ring, if you collect all red coins, you get a power up or an extra life.
Blue Coin: get a blue coin and you get 5 coins!
Green Shell: hold it for great swimming, or kick it.
Red Shell: hold it for greater swimming than green shells, kick it or make yoshi breath fire.
Blue Shell: kick it, holding it for even faster swimming or getting the yoshi wings.
Yellow Shell: kick it, holding it for the fastest swimming or making a yoshi ground pound.
Flashing colored Shell: gain all 3 shell ablities when yoshi eats it.
Hammer Bro Platform: when a afhb is defeated, you can ride the platform it was on.
? block: get a coin or item from it.
Buzzy Beetle shell: acts he same as a green shell. but you can only hold it or kick it.
Gold block: hit it and get loads of coins.
Gold Shell: when the shell hits an enemy, you get 5 coins as well as getting some in the trail it makes.
1up Mushroom: increases your lives by 1.
3up Moon: increases your lives by 3.
Power Ups
Super Mushroom: turn into super mario, luigi, peach or bowser.
Fire Flower: turn into fire mario, luigi or peach. you can shoot fireballs.
Super Leaf: turn into racoon mario or luigi. you can use the tail and fly.
Frog Suit: turn into frog mario, luigi or peach. you can swim faster.
Tanooki Suit: as well as turning into tanooki mario peach or luigi, you turn into a statue too.
Hammer Suit: turning into hammer bro mario luigi or peach maks you throw hammers.
Mega Mushroom
Mini Mushroom
Yoshis power ups
Blimp Fruit
Dash pepper
Boub berry
Bowsers power ups
Mega Magic
Strink Magic
Frog Pot