What does Available after Apprenticeship even mean?

Ok, not trying to be upset but oh boy I could swear up a storm.

Let me explain, so I been playing Hearthstone for at lease 2 yours now. I was never good at whole Play mode after playing Knights oh the Frozen Throne And got my packs from it. I went to open and I came across “Available after Apprenticeship” This cone fuse me but no matter I still needed to face the Lich King. After I keep losing I decided to look at other builds to see how they face him.

This lead to my second Issue, Wild cards. I couldn’t craft them nor get my hands on them, so I look up how to get into the wild and I found I have to get into the wild I frist have to get to rank 25, get my first wild card then I can get in.

I work hard and finally made a deck that got me to rank 24 But still I can’t open packs and I still can’t get my hands on wild cards. Even worst is now many of the cards I been using is now saying I have to be rank 25. I am rank 24…Is this a bug? Did I miss something…

Can someone help me understand why I can’t even open the packs I bought and collected.

Thank you for your time.