The update version you want is 1.4.1 (v196608) . Some sites offer v1.4.0 which lacks the "xin" (new) playable characters—only v1.4.1 includes Amy, Knuckles, and Tails.
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Sonic Frontiers represents a massive leap forward for the Blue Blur, bringing high-speed action to an open-zone setting. Since its release, the game has been significantly improved through free updates, culminating in the massive DLC.
On your PC, open the newly appeared Switch drive and navigate to .
The standard file format for digital Nintendo Switch games. Unlike XCI files, which mimic physical cartridges, NSP files are optimized for digital distribution and are generally smaller as they lack unnecessary "padding".
Sonic Frontiers Switch NSP + DLC + Update: The Ultimate Romhacking and Emulation Guide
An alternate ending/storyline that takes place in the final area, Ouranos Island.