Not a good idea to download WhatsApp Delta, here's why?
WhatsApp Delta has recently become popular because of the features it offers like automatic replies, compatibility with all sticker apps, the ability to send large video files (as large as 50MB), text fonts, themes, the option to remove the forwarded message tag, etc. You can also hide typing notification and online status on WhatsApp Delta. Amongst all this, the most popular feature on WhatsApp Delta is the ability to modify/edit a sent message.
You cannot download WhatsApp Delta from the App Store or the Play Store since both these app stores do not allow modified apps. You can download the WhatsApp Delta mod from third-party app stores and the APK file for the app is also available online. Most of these third-party app stores show high ratings for WhatsApp Delta making most people feel that's it is safe to download and use it. The app can run on any phone that's on Android 2.2 and above.
WhatsApp does not allow modded versions of its apps and can permanently ban accounts if users are found using these. The platform has stated on its FAQ page that if users do not switch to using the official app after being temporarily banned, they can get permanently banned from using WhatsApp.
WhatsApp calls modded apps like WhatsApp Plus and WhatsApp Delta/GB WhatsApp unsupported apps and has advised users to steer clear off these, warning them that since the company does not support third-party modded apps, it cannot offer security on these.