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When you open something sealed, you're unsealing it or breaking a seal.
開封 generally refers to opening something sealed, like opening a letter or package.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
開封前の商品であればいつでも返品可って書いてあるけど、開封後に中身が壊れてたり、その商品が好きじゃなかった場合はどうなんだろう。
It says I can return unopened products at any time, but what if I opened it and the stuff inside was broken or I didn’t like it?
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up whatever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.