iCloud, and then I used it up, and I will not renew the photos in iCloud later...

Your decision to stop renewing your iCloud Photos storage after exceeding your current plan's limit will initiate a specific, managed process governed by Apple's operational policies, with significant implications for your data accessibility and device functionality. The core mechanism is that iCloud Photos is a synchronization service, not a standalone backup; it mirrors the state of your photo library across all devices signed into the same Apple ID. When your iCloud storage becomes full and you choose not to purchase more, the service can no longer upload new photos or videos from any of your devices to the cloud. Crucially, existing photos and videos already in iCloud will remain stored there, but they become frozen in their last synced state. New captures or imports will reside solely on the device where they were taken, creating a fragmentation of your library. This fragmentation means that photos taken on your iPhone will not appear on your Mac or iPad, breaking the seamless cross-device access that defines the service.

The immediate practical consequence is that your devices will persistently display storage-full alerts, and the Photos app may cease backing up your recent moments. Over a longer period, a more critical process may engage: if your iCloud storage remains over capacity for an extended time, Apple's systems may prevent your iCloud account from backing up any of your other app data or device settings, as the backup service also consumes the same pooled storage. This can leave your device's configuration and app data vulnerable if your hardware is lost or damaged. Furthermore, you risk a degradation of your existing library's integrity. Should you begin deleting photos locally on one device to free up space, those deletions will sync to iCloud and, consequently, propagate to all your other devices, potentially removing the only remaining copies of those images if they were not archived elsewhere.

To manage this scenario without renewal, you must actively decouple your local device storage from iCloud's synchronization control. The definitive action is to download and retain a complete, original-resolution copy of your entire iCloud Photos library to a trusted local system, such as a personal computer with sufficient hard drive space, using the Photos app on macOS or the iCloud for Windows application. This creates an independent archive. Subsequently, you could disable iCloud Photos on your devices, which would convert each device's library to a purely local collection, ending the sync but also permanently severing the library's unified structure. An alternative, less drastic approach is to meticulously curate your iCloud library by deleting large files like videos or redundant screenshots directly through iCloud.com, which can free up enough space to restore basic sync functionality without increasing your storage tier. The central analytical point is that iCloud Photos operates as an integrated system; opting out of its storage component necessitates a deliberate and potentially technical migration project to preserve data cohesion, moving from a managed, cloud-centric model to a user-maintained, local-first data architecture.