If an installer or app requests your Apple ID credentials to bypass a signature check, never use your primary, modern iCloud account. Use a disposable dummy account instead.
The retro iOS community has built several repositories dedicated to preserving old application versions. 1. The Internet Archive (Archive.org) ios 7 ipa archive
The iOS 7 IPA archive is a vibrant, community-led effort. You are not alone in this quest. Key communities include: If an installer or app requests your Apple