With help of this guide and cheats, I beat the game under 2 hours easy even with backtracking and reloading saves, while also carrying the cone from the beginning to the end. So I got two hardest achievements in a single playthrough.

Cheats:
sv_cheats 1; god; sv_cheats 0
sv_cheats 1; noclip; sv_cheats 0

and I used this command in console to check timer (Thanks to Terrors):
achievement_hdtf_two_hours_state

Very great video. Thanks.

Good job bro