WotLK Onyxia's Lair (Level 60)

[Blkunxpd]

. .

[Persivaln]

If you meet all requirements for them - you will get such achievements.
But just buying item from store won't grant it.

[Blkunxpd]

. .

[Persivaln]

I don't spam for count, bruh(. Requirements can be found on database sites or just follow guide about it. But if it is old content that was removed/remade, chances are high that you won't get achievement, for it being impossible to complete due to key part non existing in game.

[Sixtyninee]

The achievements that were disabled beyond a specific patch aren't obtainable anymore. It was all thoroughly tested with every realm that went from vanilla to wotlk progression. For example, I have Hand of A'dal but I also have the new quest to start the chain that doesn't award the title and the achievement is for earning the title.

[Blkunxpd]

. .

[Mercy]

Well, I have the achievement for "Hand of A'dal" on my shaman, but I don't have the title and never did? Earned September, 2016 on Deathwing/Icecrown

This was due to a bug. It has long since been fixed.