One way to launch the game - the digital copy must be in your Steam library:
1. Unpack the resources.
2. Name the folder as you like (Half-Life 2 006) and move it to \Steam\steamapps\common.
3. Launch Steam (login is required) at first and only then launch the game with hl2 .exe or the shortcut.
No login/digital copy (HL2 for HL2-2707 / EP1 for HL2-2803) - you'll get only some maps of Chapter 1/6.
If select in Phoenix manually Base Source Engine 2 (Source 2006) instead Source Engine (Source 2004) then in-game HL2 version be Source 7 2803 - but it works in fact without any benefit of Source 2006 developer.valvesoftware.com/wiki/Source_2006 - fixed bugs only - Source 2006-EP1/2007-EP2 have not a command "mat_phong" unlike Source 2013-HL2/EP1/EP2, but the Phong shading is seen unlike HL2.
Since the unpacked \hl2\maps with .bsp and \hl2\maps\graphs with .ain have a different modified time, you'll recieve the infamous problem "Node Graph out of date. Rebuilding" in the beginning of each maps, and related one "A.I. Disabled" after loading your saves: all you have to do is set the modified time of .ain to .bsp ones (a deleted scene "intro .bsp" youtu.be/pUv9zOtY-do is optional) - not a second newer - with BulkFileChanger nirsoft.net/utils/bulk_file_changer.html (actions - change time - pay attention on GMT).
Steam-Properties-Launch options/Shortcut-Properties: +r_lod 0+cl_detaildist 10000+rope_wind_dist 10000
r_lod 0 - "will effectively make every render as if you are close to them"
cl_detaildist - "distance at which detail props (grass) are shown" 100 : 1
rope_wind_dist - "applying small wind gusts to ropes" 100 : 1
Access to all chapters: sv_unlockedchapters 15 /to all maps: map "name".
Text language: Win+R - regedit: HKEY_CURRENT_USER\SOFTWARE\Valve\Steam\steamglobal
Speech language (hl2_sound_vo_language_000-006-dir .vpk) depends on Steam internal settings and must be auto downloaded into \Steam\steamapps\common\Half-Life 2\hl2 - it needs to be extracted (open language_dir) with GCFScape developer.valvesoftware.com/wiki/GCFScape to \Half-Life 2\hl2_language
2004 does not use \sound\combined unlike 2005-2022 - non-English speech may varies.
Source 2004/2006 use natural glossy shaders of weapon/crowbar-HL2-headcrabs/Dog unlike 2007/2013.
MSAA has rare artefacts (red/white lines) unlike MSAA+SGSSAA or SSAA or SSAA+MSAA+SGSSAA with nvidiaProfileInspector - use "Enhance the application setting" while MSAA in-game (4x nvidia) must be on.
3D sound is activated with "snd_digital_surround 1" unlike 2004-2005. Since Vista, it needs to be restored with Creative ALchemy, but standart buffers/duration 4/25 (delay 100ms - alike input-lag) give lots of clicks here (5.1 works) - use 3/5 (elusive delay 15ms) instead, tested with X-Fi Ti CMSS-3D Headphone.
Since 2459 a "sunken wheels issue" at Chapter 1 (Strider) is appeared - a fix is within client/server .dll.
2707 has a "no shadows issue" at Chapter 6 in DX9 - can be fixed with shadow_ps20 .vcs from 2733 which is identical with 2803/3224/3264 while shadow_vs20 .vcs from 2707 is identical with 2733/2803/3224/3264.
Source 2006 has a heavy "water reflection issue" at Chapter 4 (Station 7) in DX9 - 2013 has the light one.
Shader Model 3 (DirectX 9.0+ / mat_dxlevel 95) is available since 2707.
HDR/Bloom are useless for HL2 Source 2004/2006/2007 - have no HDR-maps yet (Chapters 5-9a/part1).