Are the functions on WeDJ for iPhone the same as those on WeDJ for iPad /WeDJ for Android?

No. The functions on WeDJ for iPad and WeDJ for Android are different from those on WeDJ for iPhone. Visit the following product pages for details.

WeDJ for iPad
https://www.pioneerdj.com/en/product/software/wedj-for-ipad/dj-app/overview/
WeDJ for Android
https://www.pioneerdj.com/en/product/software/wedj-for-android/dj-app/overview/