inorganic chemistry - Manganates (II)

I want to ask about character of manganese(II) compounds. I read that $\ce{MnO}$ is basic, just like $\ce{Mn(OH)2}$. I started doing research and I read ions like $\ce{MnO2^{2-}}$ and $\ce{HMnO2^-}$ exist too, but how? Are they related to reactions in solid state? Manganese(II) hydroxide isn't amphoteric like aluminium hydroxide so it's really confusing for me. I also found reaction that "confirms" amphoteric character of manganese(II) oxide

$$\ce{Mn(OH)2 + 2NaOH -> Na2[Mn(OH)4]}$$