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