Learn Finnish: Sinun kannattaa pyytää kunniamerkki itse majesteetilta. - You should ask for the decoration of honour from the majesty herself.

When used to mean 'the X itself' or 'X in person', itse acts as an intensifying appositive right before the noun. In this specific role, it is uninflected. It stays as itse while the following noun takes whatever case the sentence requires (here, the ablative -lta).

Could I put itse after the noun instead, like majesteetilta itseltään?

Yes, but then the grammar changes. If you place it after the noun, it behaves like a normal pronoun: it has to match the noun's case and take a possessive suffix. The uninflected shortcut itse only works when placed immediately before the noun.

Why is the object kunniamerkki in its basic dictionary form rather than the genitive kunniamerkin?

The sentence uses the necessity structure sinun kannattaa ('you should' or 'it is worthwhile for you'). With necessity verbs like kannattaa, täytyy, or pitää, a complete object doesn't take the typical genitive -n ending. Instead, it takes a form that looks exactly like the basic nominative case.

Why is majesteetti in the ablative case (majesteetilta)?