Owlboy

The game is 100% completable without the last missing patch. However, there are some caveats.

For the most part game runs and plays well. There is one boss fight in the late game, where performance tanks heavily during one attack. The performance drop occurs AFTER you've avoided the attack, so it's not problematic. It happens every time the boss does the attack. Interestingly, when dodging the attack, performance won't drop.

On one occasion when attacking a breakable object the playable character glitched through the ground and fell through the map, forcing a game reset.

Apart from that the game also crashed twice, once from the loading screen, and once after finishing the final boss. The crash on the final boss seems to be consistent, and was reported by other players as well. Due to the crash the final boss must be replayed to get to the ending. The second time the boss was beaten the game progressed without a crash.

Players have also reported on the internet how they experienced issues with 100% completion due to bugs. Patch notes for v1.0.2 (which is on the cart) state that the bugs were fixed, and a "input code" was added that can help achieve 100% completion if a bug is encountered (or if you're too lazy to grind the missing collectibles). This "input code" works off of the cart.


Second tester's playthrough:

Completed 100% with version 1.0.2 on the cartridge. Obtained all coins in every area, obtained all items from the shop, obtained the 3 golden discs, the hidden key, completed the mini game and completed the game.
Didn’t experience any issues getting 100% for this game.

As stated on the previous test, the game does crash, five times during this playthrough. Was able to load the game and get back to where we left off within a few seconds. Happened totally at random and can’t pinpoint what would have caused the crashes in the first place.

The second issue is slow downs or frame rate drops. There seems to be some very minor hiccups during the game, nothing too noticeable until the worm boss. This particular boss has major slow down when it blows fire at you. It stabilizes once the fire disappears, but be aware the slow down will occur. It doesn’t cause any issues with dodging the attack or any issues of getting harmed because of the slow down, so it’s not that big of a deal.

A secret area unlocked once all items are obtained for 100% (Won’t say what is included or anything due to spoilers) but for some reason, when entering this area for the first time, whenever trying to jump the character wouldn’t jump. Reloading the last checkpoint fixed it.

Mostly the game performs great and works great from the cartridge.