IOS(Requires Jailbreak): https://www.mediafire.com/file/mmog8d8xm452md4/%25E6%2588%2591%25E7%259A%2584%25E4%25B8%2596%25E7%2595%258C_Lite%25E7%2589%2588_Minecraft_-0.2.1.ipa/file

Android: https://androidapksfree.com/minecraft-pocket-edition-demo/com-mojang-minecraftpe-demo/

IOS Tutorial:

Android Tutorial:

If you are on android and on the same google account that you downloaded the game before it was deleted you can still install it via google play using this link: https://play.google.com/store/apps/details?id=com.mojang.minecraftpe.demo