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