Here is the full list of all 42 STEINS;GATE achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Unlocked all Achievements.
[Phone Trigger] Received all 13 RaiNet episode summaries.
[Phone Trigger] Received 4 songs from a chaotic head.
[Phone Trigger] Received all Gero Froggy wallpapers.
Unlocked all CGs.
[Phone Trigger] Received 3 wallpapers of characters from a chaotic head.
[Phone Trigger] Asked by Kurisu to buy cup noodles twice in a row.
Learned about Luka's relationship to his sister.
[Phone Trigger] Offered tea by Faris.
Completed all endings.
Unlocked 75% of CGs.
Reached Kurisu's ending.
[Phone Trigger] Learned why Mayuri started making costumes.
Reached Mayuri's ending.
Reached Steins Gate.
Made 10 mistakes while attempting to set the PhoneWave (name subject to change)'s timer.
Reached Luka's ending.
Reached Faris's ending.
[Phone Trigger] Received an unusual proposition from Suzuha.
Made friends with Kurisu via email.
Chapter 9 Clear
Chapter 7 Clear
Chapter 8 Clear
[Phone Trigger] Cleared someone's mail without reading it.
Chapter 6 Clear
Reached Suzuha's ending.
Unlocked 50% of CGs.
[Phone Trigger] Received 2 Upa wallpapers.
Chapter 5 Clear
Chapter 4 Clear
Unlocked 25% of CGs.
[Phone Trigger] Ignored a phone call.
Chapter 2 Clear
Chapter 3 Clear
[Phone Trigger] Replied to an email.
Chapter 1 Clear
[Phone Trigger] Changed ringtone.
[Phone Trigger] Changed phone wallpaper.
[Phone Trigger] Viewed email send history at least once.
[Phone Trigger] Read an email.
Prologue Clear
Started Steins;Gate.