Spoiler Alert if you havent played the original gameboy game!

I know there were some secret seashells that you can only get with the flying pidgeon. And if you dont have the pidgeon anymore then theres no way to get them anymore. 

I dont remember if there were any secrets that you had to get before returning the bow wow.. does anyone remember? 

Were there any other things that I need to make sure to do to prevent having an incomplete game?

There was nothing missable in the original game with BowWow. The photograph came afterwards, and if you missed the chest in the swamp, the boomerang or the fire rod will kill the flowers there.

Any for your information, it's a rooster, not a pigeon. Sheesh.

Weren't many of the pictures missable? Like Malon falling on top of you, only gettable when she follows you.

I just went to the seashell mansion. And you get a prize with each increment of seashells that you find. I don't know if it's an issue in this game, but I remember on the Gameboys version if you didn't collect the prize for one increment and then you got enough seashells to get the prize for the next increment then you basically missed out on the prize

Go play some mario maker 2, getting pretty negative up in here lol

Where is the game breaking mistake?

If you die whatsoever in the original, you don't get the full ending, I wonder if they kept something for that

One that I recall is that there is a seashell in an underground cave by the castle. You need the flying rooster to get it. If you don’t get it during the short time you have the rooster then you can’t get it forever. I didn’t play the dx version, so don’t know if they kept it that way. 

I just remember playing the game once and not being able to get the level 2 sword because of that mistake 

For some reason I was thinking there was something you could only do with bow wow or with Marin, but I could be remembering wrong
 

There were 26 seashells in the original. You only need to get 20 for the sword.

You can get the level 2 sword well before you get the flying rooster (all seashells in chests after you get the sword become 20 rupees, FYI).

I don’t know if the photographs are still in it, but if so, there are several you need to get when you have Marin, and you need to get the one with Richard before opening the gate to Kanalet Castle.
 

Game breaking or completionist ruining?

Are you sure about this? Because when I was a kid, I’m fairly certain I used the shovel on every single diggable spot on the map several times over. And found all bomb-able walls.

Is it possible that this changed between the original and the dx version

 

Definitely. I've never owned DX. Like already mentioned in this thread, you can get Level 2 sword before the 7th dungeon.
You can also miss the ones at Seashell Mansion when you have exactly 5 shells, and when you have exactly 10 shells.

Phew, I was worried that returning bow wow was gonna mess something up for me.

I also don't think I've died, as I always save right before a boss right and if I die in them, I just upload the save file from before the fight. Other than that I haven't died yet. Does this mean I have a zero death run going? Is there anyway to tell? lol

Yea you played this back in the day way too much to probably enjoy this remake to the extent 99 percent of the popularion that buy it will

I didn't get that far in the original so I don't know if it was the same, but I know in the remake if you're talking about the shell I think you're talking about, the one just to the southwest of the castle, you can get there with the hookshot now, so you don't NEED the rooster to get there anymore.

Yes actually, if you look at your save file when you first boot up the game, somewhere in the bottom left of it should be a little gravestone with a number next to it. If that number says 0, then you're in business.

Ohhhhh, then I'm good to go!