Here is an example :
| Global number Sprite01 = 0
| Global number Score = 0
+ System: On start of layout
----+ System: Score > 2
-----> Sprite01: Set animation frame to Sprite01
-----> Sprite01: Set Visible
+ System: Score > 2
+ System: Trigger once
-> System: Set Sprite01 to choose(?0?,?1?,?2?,?3?,?4?)
-> Sprite01: Set animation frame to Sprite01
-> Sprite01: Set Visible
Perhaps you want to change the name of your global variable so it does not have the same name as your sprite (which may cause confusion).
Your global variable "Sprite01" you mention is a supposedly a number.
Make sure the it is well set to be such.
At worst, set the value as int(choose(0,1,2,3,4)).