How to update iPhoto to 64 bit

iPhoto was discontinued 6 years ago and replaced with Photos.

It is easy to switch to Photos:

Launch Photos with the option key held down. From the dialog, choose your iPhoto Library. Photos will create a new Library with your iPhoto media.

iPhoto is a 64-bit application but it needs old iLife system frameworks, that are no longer available on the newer systems since macOS 15 Catalina, because the older system frameworks are 32bit. There is no way to run a full iPhoto version on the new systems, because the system does no longer support it.