Is there any way to access the lost levels

[poke_ravi]

without having to play through the whole game.... especially since I've played the game before when it originally came out.

[Tsuki Zero]

You can either beat the game once... Or unlock Hectic and access level select via features... Or add -warp 34 to the command line to start right on it (and optionally -skill 1 to 4 to select your difficulty)

[Plodo]

You can also use a password to get to MAP28. Beat that and you’ll unlock it. Worked for me on Xbox one version.
https://doomwiki.org/wiki/List_of_Doom_64_passwords

W83M 7H20 BDY0 N9VB
Is probably the easiest/fastest to go with. All demon keys and weapons. And it’s on easiest difficulty.

[Elkondo]

You can use console commands to unlock features menu and select a map.

[yummy]

Originally posted by Plodo:

You can also use a password to get to MAP28. Beat that and you’ll unlock it. Worked for me on Xbox one version.
https://doomwiki.org/wiki/List_of_Doom_64_passwords

W83M 7H20 BDY0 N9VB
Is probably the easiest/fastest to go with. All demon keys and weapons. And it’s on easiest difficulty.

That code worked, and it was pretty fun. I already beat the game, but did not collect all 3 keys. This code did not unlock the cheevo. But it still was fun.

[Plodo]

Originally posted by yummy:

Originally posted by Plodo:

You can also use a password to get to MAP28. Beat that and you’ll unlock it. Worked for me on Xbox one version.
https://doomwiki.org/wiki/List_of_Doom_64_passwords

W83M 7H20 BDY0 N9VB
Is probably the easiest/fastest to go with. All demon keys and weapons. And it’s on easiest difficulty.

That code worked, and it was pretty fun. I already beat the game, but did not collect all 3 keys. This code did not unlock the cheevo. But it still was fun.

Good to hear!
I was at work so I couldn't test myself.
The achievement for all 3 demon keys didn't unlock? It probably unlocks when you actually pick up the third one. So only a password won't do.
But it does unlock the Lost Levels for people who don't want to play the whole game to access them. I just tried on Steam version.

If you want to unlock the achievement for the demon keys try this password: VR9M QK24 BDM1 D9VB
You'll warp to the level which has the third demon key. You'll have all weapons and the other two demon keys. If you don't know how to get the third key I'd recommend youtube:
https://www.youtube.com/watch?v=Xd2a1K6USBc
the guide for the third starts at about 1:00
(edit: this works as well. just tried this myself and got the achievement)

Here you can generate an in-game password for anything:
http://eternity.mancubus.net/d64pw/
just found out about this today.