Here is the full list of all 20 Emily is Away achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Complete Chapter 5
Complete Chapter 4
Complete Chapter 3
Complete Chapter 2
Use the Portal Icon
Use the John Cena Icon
Use the Undertale Icon
Use the Sigur Ros Icon
Use the Nyan Cat Icon
Use the Elegy for a Dead World Icon
Use the Dota Icon
Use the Stanley Parable Icon
Use the Fallout Icon
Use the Isaac Icon
Use the Half-Life Icon
Use the Doge Icon
Use the Zelda Icon
Use the Kappa Icon
Complete Chapter 1
Use the Clippy Icon