Is Lanthanum a real lanthanide element ? Why? or Why not?

Lanthanum is

Lanthanides are

Which is the non-lanthanide element ?

Why do radioactive element decay?

Which of lanthanides is man-made element?

Which of the following statements concering lanthanide elements is false ?

Why is the separation of lanthanide elements difficult?

Why are transition elements so named ?

Which of the following Lanthanides element do not show stable +4 oxidation state?

What are the characteristics of th transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?