The only differences in Yii 2 is that its much simpler due to available functions in the Model class for loading and validating models.
Yii Framework Wiki
Wiki articles in category Tutorials tagged with "validation"
Showing 1-4 of 4 items.
How to display page on fancybox...using CHtml::ajaxlink with yii validation
1) include the fancybox extesion otherwise fancybox js
A simple way to get Yii client-side form validation run when submitting by ajax
A time ago i've met the issue that Yii doesn't run any client-side form validation when submitting the form by CHtml::ajaxSubmitButton. The small javascript below helps to fix it.
Working with radiobutton list
This is a tutorial to work with radioButtonList which will handle enum datatype. Form design and validation both are detailed here.