Older versions are no longer on the Google Play Store. Reputable archiving sites include:
Opera Mini has a legendary status in mobile history, acting as the primary gateway to the internet for millions, particularly in emerging markets, between 2005 and 2015. While the modern Opera Mini for Android continues to exist, old versions—specifically those from the Java ME (J2ME) and early Android eras—are still sought after for their extreme data efficiency, low resource usage, and minimalist design. Opera Mini Old Virsion
A total rewrite that introduced "Overview" mode, letting users zoom in and out of full desktop-style web pages. Older versions are no longer on the Google Play Store
What is your (saving data, running it on an old phone, or using a specific UI)? A total rewrite that introduced "Overview" mode, letting
Knowing this, I can tell you if a specific version like 4.5, 6.5, or 7.6 is the best choice.