I actually didn't know this. Are you sure the bolded is true?
Yes. Ive platinum’d the game.
Once you beat the 3rd boss and start in Biome/Level 4, if you die again you start in Biome/Level 4. You don’t go back to Biome/Level 1.
You always start in Biome/Level 4 after you beat the 3rd boss
And once you beat the first boss, you can use a level portal to reach level 2 without doing all of level 1.
Same as when you beat the 2nd boss. 4th/5th boss etc.
Once you finish the game, you can choose if you want to start in Level 1 or 4 to collect the key items for a 2nd/Secret ending.
The game also saves all you key items, weapon progress.
Theres alot of misinformation mostly by people who don’t even have the game or console lol….