Do these games contain build-in cheat codes (unlimited ammo, health etc.)?
I would like to experience these games that way at least (did the same with original Doom, Quake, Duke Nukem 3D).

Assuming these are being released as the original PC versions did, then I know that Resident Evil 2 has an unlimited ammo cheat. The rest didn't have cheat codes.

There is no cheats. You can get a special weapon for completing the game, and the rocket launcher if you finish the game without saving (if nothing changed from the og pc version). But as far as I remember, no cheats available for RE1

I can't recall exactly how Classic Rebirth works. At least 1 or 2 games of the original trilogy have a debug menu with cheats. Maybe all of them.

There's also something called Cheat Engine where there's somebody who makes tables for all 3 games of the trilogy for Cheat Engine on the fearlessrevolution forum.

This all reminds me of the recent Metal Gear Solid remasters, and many other games. The official release comes nowhere near as good as what can be done by the community.

There is no special code you can enter in the inventory screen that activates infinite ammo how RE2 has. Sorry.
The mediakite version (which gog does not use, has a "bonus" folder with savegames that have every bonus weapon unlocked. Not part of this gog release.

Some corrections:
finish under 5 hours -> infinite magnum
finish under 3 hours -> infinite rocketlauncher
finish under 3 hours -> infinite minimi for chris, infinite ingram for Jill
finish under ?? and all characters survive -> special key for costume change room
-> some of these requirements also need you to finish the game with all 3 characters to survive to give the bonus. I forgot which requires what. The key definitely requires that all characters survive under 5 (or was it 3?) hours.
-> saving does not matter, using a healthspray does not matter

if wrong shout me out haha!