Here is the full list of all 38 It's Quiz Time achievements.
Complete a game with 8 players
The same player answers every question correctly during All in Order
The same player answers every question incorrectly during All in Order
The same player correctly predicts that everyone will answer correctly during Trust or Bust
A player guesses only one clue during Describe It!
A player scores over 9,999 points in a multiplayer game
Complete 10 games with friends
A team of two or more players beats the leader in Showdown
A player answers correctly during Trust or Bust when all other players predicted otherwise
The same player wins three games in a row
The leader beats a team of two or more players in Showdown
Best friend fails to correctly predict player's answer in Best Friends Forever
All players answer every question correctly during the Starter Round
A player goes from last place after the first round to winning the game
Play two back-to-back games with the same players
A player correctly answers all specialist subject questions during The Big Finish
The same player is leading at the end of every round and wins the game
Complete a game with friends
A player scores over 450 points on a single question in The Big Finish
Someone calls 'Shenanigans!' during Describe It!
A player correctly guesses every clue for a subject in Describe It!
Complete a Solo Score Attack game
Complete 30 games with friends
A new player wins the game
Someone joins mid-game
No-one answers incorrectly during a round of Connections
A clue is removed during Describe It! after someone calls 'Shenanigans!'
No-one answers correctly during Trust or Bust
The same player predicts everyone will answer incorrectly during Trust or Bust
Everyone answers correctly in Best Friends Forever, apart from the best friend
The same player is chosen as the best friend by all players in a round of Best Friends Forever
The same player works alone against a team of two or more players in Showdown 5 times
All players choose the same specialist subject during The Big Finish
All players in a 4-player multiplayer game finish with over 7,500 points
Finish a Solo Score Attack game with zero points
Score over 8,000 points in the Solo Score Attack
Play on October 31st
Play on December 25th