Can I change any of the 5 finalists after the finalist phase has already began?

Absolutely. When you drag around the logos within the Ranked Logos box it will change who your top 5 designers are. By moving a designer up the ranks in the Ranked Logos box you can place them among the top 5 if you choose to.

There can be 5 designers, not logos, that can submit in the finalists phase.

For example, if you wanted to replace the designer menangan with the designer KID A, you could drag KID A's  logo in the place of menangan's logo. This is show below: