In any case, you will enjoy all Premium+ advantages immediately after subscribing! Since you switch from a Premium subscription, the amount and date of the first payment for your new subscription will vary according to the platform you use to subscribe to Premium+:
On our online shop (and on Android): When you subscribe to Premium+, you aren’t charged immediately. The date and amount of the first payment for your new Premium+ subscription are automatically calculated based on your remaining Premium subscription time at the time of subscribing.
On iOS (Apple, iPhone): When you subscribe to Premium+, you are charged immediately. If you do so before your current subscription is renewed, a pro-rated discount will automatically apply.
Yes, it’s indeed possible! You can switch back to a Premium subscription at any time. However, any change will take effect at the next payment date of your current Premium+ subscription. Meanwhile, you will continue to benefit from Premium+ advantages under the subscription terms.