Here is the full list of all 10 Let's Sing 2019 achievements.
Get 1 bronze record
Get 5 gold records
Get 10 diamond records
Sing 15 different songs
Unlock 3 avatars
Finish 50 % of the CLASSIC mode
Finish 50 % of the MIXTAPE mode
Finish 50 % of the FEAT. mode
Win 5 games in WORLD CONTEST mode
Reach level 30