This galaxy is opened up by talking to the Hungry Luma and feeding it 1,200 star bits.
Bulb Berry's Mysterious Glow
Grab the Yoshi by the start and head down the walkway past the two Choppahs and grab the Bulb Berry there. This will reveal the path to the next platform where you can grab a checkpoint and another berry and continue on. When you keep going down the next invisible path, you'll have the option to go left or jump the gap and go straight ahead. If you go straight you can grab a 1-Up Mushroom on your way. Either way will take you around to another Bulb Berry on some steps, after which you can keep following the invisible pathway. After the wooden circular bit, the path once again diverges, this time jumping across platforms straight ahead to the Comet Medal, or turning left and jumping up onto the chocolate bar platform where a Smeech is waiting.
Grab the Bulb Berry in the corner and take the path off the side of the platform, then around and past another Choppah. When you get past the Choppah you won't need the light anymore as you cross the two moving platforms to the other side where another Choppah and some green disappearing panels are. Past the next Choppah, run along the green panels quickly to grab a 1-Up Mushroom on your way to the next Bulb Berry. Grab the berry and jump up the steps where you can continue on off the far side or take the pull flowers up to another Bulb Berry. Jump across the blocks and the moving platform, grabbing another berry if you need it, and cross to the other side with the checkpoint flag.
Here you'll need to run around the pathway turning all the blue ? panels yellow. In addition to the blue panels, there are also green vanishing panels that disappear after you touch them, so no backtracking. Start out by grabbing the Bulb Berry and going straight ahead, running on the ? panel and green panels, then take a left on the invisible walkway over another blue panel out to another berry. From there cross the invisible pathway to the lone green panel with a Bulb Berry on it. Quickly grab the berry and jump off the side and continue along the invisible pathway. This will take you to another blue panel with a yellow platform on the side and a Bulb Berry. Grab the berry and continue on by jumping from green panel to green panel, then hanging a right at the invisible panel and hopping across two more green ones to the last blue panel. This creates a Launch Star in the middle of the area and all you have to do is grab the Bulb Berry next to the panel you're on and head out to it while avoiding or eating the Choppahs in the way.
In this last area, you'll see a box open to reveal a big cake, but it vanishes when you land. Grab the checkpoint and the Bulb Berry in front of you and start forward, eating the Choppah and jumping up to the right. There are no more Bulb Berries, so you'll have to quickly jump up another level then move over to the left side of the cake and keep jumping all the way to the top. When you're up there, don't waste any time, just jump right into the Power Star before your light runs out and you fall through the invisible cake.
Bulb Berry's Purple Coin Glow (Prankster Comet)
You need to get all 100 purple coins. The course is the beginning of the first star, up until where you have to hit all the blue panels to show the Launch Star. There is no time limit, so take your time and don't worry about leaving some purple coins to refresh your Bulb Berry and come back. The only other place you really have to be careful is on the green panels by the 1-Up Mushroom, because the panels never come back so try to get the two purple coins on them on your first pass.
On the platform with the first checkpoint, you should be able to see the first Green Star not far away. You can jump right out to it if Yoshi isn't glowing, but it's safter to grab the Bulb Berry there and take the invisible walkway out to the chocolate corner above the star and wait for your light to run out so you fall right on top of it. The second Green Star is by the Comet Medal. Keep jumping out past the Comet Medal and it's right there.