Hi ,
Thankyou for your fast replies.
I cannot use DDX/DDY nodes directly because editor saying “Error [ES2] (Node DDY) Node not supported in feature level ES2” and I don’t understand because opengl es2 supporting this. When I use this nodes with CustomExpression it is working 
The real problem is: When select texture sample MipValueMode to Derivative, nothing rendered on mobile device. But it is working on PC and Mobile Preview. (just rendering transparent on mobile device.)
I tried Your/RyanB’s suggestion and same problem here, working on PC and Mobile Preview but not working on mobile device. (just rendering transparent on device.)
BTW, TextureSample with MipValueMode=Deriviate and RyanB’s suggestion is not working on real mobile device. Both is working on only PC and Mobile Preview.
Thank you.