I guess that the Language package you installed does not fully support all phrases. So for the missing phrase, you can use translation feature for missing phrases. Please go to AdminCP > Localization > Phrases > Search the phrase you want to translate
Did you install brazil language package for your site? If yes, it is an issue and please submit a ticket with your site information so our support team can help you.
That is correct as some apps have their own folder for images. But, I would assume you know what images you want to transfer like profile image, cover image, etc. I did this once just to make all profile and cover images look the same and have the users upload new ones. Moving to a new system is a very expensive endeavor to transfer everything.