Can I pay subscription for an year or more, at one time instead of monthly payments?

The only plans available are all monthly subscription plans. No matter what you do, the fees will never be removed from your account in one lump annual sum. The subscription fee will always be billed monthly.

It can only be done if you purchase a sizable iTunes gift card and load the amount to you account. That way you set it and forget it, and won't have to worry about the monthly payments.