Updating iOS on your iPhone should typically not alter the fundamental functionality of the device. It's possible that there were underlying issues before this update, which you might not have been aware of previously or might not have noticed.
In general, iOS updates are designed to enhance the user experience, improve security, and fix bugs, rather than introducing major disruptions to core features. The reported issue of the screen flickering and displaying a white screen after an update is likely caused by factors that are not explicitly mentioned in your post.
iOS updates primarily focus on improving system performance, introducing new features, fixing bugs, and enhancing security. They are designed to preserve your personal data, settings, and information intact.
During an iOS update, your device's operating system is upgraded, but your personal data, such as contacts, photos, messages, and other information, should remain unchanged. However, it's always a good practice to perform a backup of your device before any major update to ensure that your data is safely stored.
It's important to note that while an iOS update itself should not alter personal details, it's possible that certain features or settings may be adjusted or improved with the update. In such cases, you may need to review and adjust specific settings to match your preferences after the update.
Always make sure to read and understand the update details provided by Apple before proceeding with an iOS update, and follow best practices such as backing up your device to minimize any potential risks or complications.

📱Facing iPhone heating issues? Here's what worked for me on my iPhone 12 Pro:
1️⃣ Backup on iCloud/iTunes
2️⃣ Log out of Apple ID
3️⃣ Erase (Keep eSIM Data)
❌ DO NOT restore from backups! Set up as new iPhone. Wait 2-3 days - no issue! That Indicates...
✅ No hardware/ iOS issue
Now...
📦 Restore data gradually
🔍 Find app/settings causing heat

My experience says this is purely caused by some third-party app that you may have installed.
I am not aware of the ambient temperature in which you are using the iPhone. However --> Keeping iPhone, iPad, and iPod touch within acceptable ...
Store the device where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.
Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behavior to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures. Using an iOS device in very hot conditions can permanently shorten battery life.