Your research questions/aims can appear in any form, and certainly do not need to be expressed in the form of testable hypotheses.
It will most likely change extensively during the first several months of your Ph D programme.
Nevertheless, at the stage of application it is an essential document that helps evaluators make their decision in relation to your application.
You should identify the method or methods you propose to use, and justify these choices - i.e., explain why this method is being used in preference to others.
You should also provide details of your proposed sample/s (numbers of respondents and type of sample) and/or secondary data sets, and again offer justification for these choices.