Answer 1

Hi Isaac,
SL stands for SoloLearn, and Code Playground (https://www.sololearn.com/Codes/) is the part of the platform where we can write, test and save codes in our own profiles.

Also I think it would be more appropriate to put Python in the tags as an additional to 'reverse' up there ☝

It helps to clarify language context ...

Answer 2

That's where SL code playground comes handy at.