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.
Unlocked all CGs.
Completed all endings.
Reached Steins Gate.
Reached Kurisu's ending.
[Phone Trigger] Cleared someone's mail without reading it.
[Phone Trigger] Received 2 Upa wallpapers.
[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.
[Phone Trigger] Received all 13 RaiNet episode summaries.
Made friends with Kurisu via email.
[Phone Trigger] Offered tea by Faris.
[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.
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 Luka's ending.
Chapter 7 Clear
Reached Faris's ending.
Reached Suzuha's ending.
Chapter 6 Clear
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.