Meaning of duplicated predicate quantifiers

Question

What is the meaning of duplicated predicate quantifiers? Examples:

$$ ∃x\ ∃x\ ∀x\ ∀x\ P(xy) \\ ∀y\ ∀x\ ∃x\ ∀x\ ∃x\ ∃y\ ∃x\ P(xy) \\ ∃y\ ∀y\ ∀x\ ∃x\ ∃y\ ∀y\ ∀x\ ∃x\ ∃x\ P(xy) $$

Answer 1

The quantifier closest to the quantified variable dominates any previous quantifiers.

The first is equivalent to $\forall x P(x, y)$, with $y$ unbound.

The second, then, is equivalent to $\exists y \exists x P(x, y)$.

Answer 2

Multiple quantifiers of the same variable are not wrong but they do not change the validity of the sentence after the first quantifier, and this is because $\forall x P(xy)$ does not depend on $x$. Hence if you add $\exists x$ of $\forall x$ in front nothing changes. It would only change if $x$ was a free variable in the sentence.