Take a look at this http://discuss.cocos2d-x.org/t/cannot-compile-project-for-android-not-a-valid-android-target-platform/22349

I solve this but new problem occurred. I tried to compile with only using cocos helper google play services it works but when I added facebook it gives error when compile.

[dx] UNEXPECTED TOP-LEVEL EXCEPTION:
       [dx] com.android.dex.DexException: Multiple dex files define Lcom/facebook/AccessToken$1;
       [dx]     at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:596)
       [dx]     at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:554)
       [dx]     at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:535)
       [dx]     at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:171)
       [dx]     at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
       [dx]     at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
       [dx]     at com.android.dx.command.dexer.Main.runMonoDex(Main.java:303)
       [dx]     at com.android.dx.command.dexer.Main.run(Main.java:246)
       [dx]     at com.android.dx.command.dexer.Main.main(Main.java:215)
       [dx]     at com.android.dx.command.Main.main(Main.java:106)
       [dx]

BUILD FAILED
../sdk/tools/ant/build.xml:888: The following error occurred while executing this line:
../sdk/tools/ant/build.xml:890: The following error occurred while executing this line:
../sdk/tools/ant/build.xml:902: The following error occurred while executing this line:
../sdk/tools/ant/build.xml:283: null returned: 2

Total time: 48 seconds
Error running command, return code: 1.

Did you use our facebook plugin from the helper?

Yes, I watched video, I did exactly same things.

Does Facebook work for you in a fresh project on its own?

I didnt try in fresh project but I added Google play services it works.

Try facebook on its own to see if you can get that to work