Have you read through the documentation? The answers are there for the majority of your questions.
For #1, this is a 2 part question. first is how do you translate the content into different languages? You can do this by going to Pages app and in the bottom of the content tree, select a different language. When you navigate to a page in the content tree it will say something like this has not been created for spanish, do you want to copy the content from english or create a blank page? Once the actual page is created in the language you want, then go in and edit the content with the proper localized content.
Second part of the 1st question is how can you translate your dropdown values? Use macros in the values like so:
For #2 & #3 see #5.
For #4 if there is hard coded text in the webpart (typically not the case with the out of the box webparts) you will need to tell the webpart to use a resource string vs. an actual text value. So this, in most cases, would require a code change. It could also just require a configuration of the default property values to use a localization macro.
For #5 when your site is set to be multi-lingual the text fields which are displayed to the end user will have a globe or a large + that in the upper right corner of the textbox. Click this and enter the label values in your different languages.