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