Is it possible to pay for a year of an upgraded plan rather than pay .99 every month?

No, it is not possible, see -> iCloud+ plans and pricing -> iCloud+ plans and pricing - Apple Support

• You can upgrade to iCloud+ from your iPhone, iPad, iPod touch, Mac, or PC. After you upgrade, you'll be billed monthly.

Only by using Apple ID balance to prepay it; click here and see what options are available in your country. It'll be applied first whenever allowed, not just for the subscription.

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