Here is the full list of all 13 Super Picture Cross achievements.
Completed your first puzzle
Completed How To Play
Completed 5 puzzles
Completed 10 puzzles
Completed 20 puzzles
Completed 50 puzzles
Completed 100 puzzles
Completed a Small puzzle
Completed a Medium puzzle
Completed a Large puzzle
Completed 1 puzzle of every size
Completed all Curated puzzles
Discovered & Completed a puzzle