Feature temporally free in iphone app

It's possible to have a free feature in my iphone game and then charge people for 开发者_StackOverflowit after some time trough an in app-purchase?.

Also, It's possible to change the price of an in-app purchase after it goes life ? ( for example, make an in-app purchase free and then change its price weeks ater the purchase went live).

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Based on THIS:

In-App Purchase can be offered in both free and paid apps—no free In-App Purchases are available.

You cannot set your in-app purchase FREE and then change it to paid, beacuse you cannot set an in-app purchase price less than $0.99..