Best practices: keyboard dismissal and button display in mobile apps

We have both iOS and Android apps with forms in multiple places, and are looking for an appropriate UX pattern for continuing when the form is complete.

Example: On the login screen, the user must type both a username and password, and then trigger the login action.

  1. Should the login button "float" above the keyboard? Only when the last field is active?
  2. Should the keyboard dismiss whenever one taps outside of it?
  3. Should the "return" button in the keyboard say "continue" when the first field is active and "login" when the final field is active?

This seems like such a standard use case that the behavior should be defined and standard for both iOS and Android platforms, but I'm struggling with finding it documented anywhere!