Can you publish a game on both platforms (iOS and android) with the same build? or do you need to make a build for each platform?

Questions & Answers
1

I wanted to know if you can publish on both platforms with the same build.

2

No, this is no possible, because each store defines a diferent format for its bundles, for a Play Store Build you’lll need an “aab” format while in the App Store you’ll need a “ipa” (or some other) format.