I think sololearn woundn't support APIs like User Location and web storage as a typical browser can, there might be more but I haven't tested it yet.
Namit Jain those stuff are game-engines and GUIs, why would sololearn support those in the first place?
codeplayground was supposed to test some code quickly.
Yes they are so many things sololearn do not support in html5,
Like <link rel="favicon" >
And most meta tag,
But you can include them in your code here.
Just that they won't actually do what they are supposed to do.
No. It depends on your phone.
See this to know what sololearn supports or doesn't support on your phone.
You can upgrade the WebView of your phone for more features.