Several subscriptions although I only need 2

Hello everyone, I have developed an app and actually only have 2 subscription models, one for a monthly subscription and one for a yearly subscription.

For the start I created these two subscriptions as an offer, then my customer wanted to create the actual price, so I created 2 more subscription models (monthly and annual).

At first I thought that I would change the price of the first two subscriptions, but since I wasn't sure whether the first buyers would have to pay the new price, I created 2 new subscriptions.

I let the respective subscriptions appear through a third party provider as I need them. But unfortunately you could simply change the subscription to the subscription with the lowest price in the store yourself. I would like to avoid that.

My question now is, could I simply change the price and the new buyers pay the new price but the previous buyers continue to pay the old price?

And if so, could I deactivate all other subscriptions and would the buyers of the deactivated subscriptions continue to pay this price and not the price of the active subscriptions?

It would be really great if you could answer these questions for me. Thank you very much.

Several subscriptions although I only need 2
 
 
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