Crop classification

I followed the tutorial in EO college for the crop classification using sentinel1 toolbox and I come across some of the misunderstanding in that tutorial as the following:

  1. in the first step, he used the band math to create layer stack as the following. it seemed that he took bands from ERS(VV for the same scene) to the HV polarization.


So my question could I use Radar,coregistration,stack tools, create stack instead from what he used.

This is the link of the tutorial

Moreover, when it comes to the classification as shown in the following picture,
the ROI mask is not active to add the name of the mask

Last but not least, he used ESRI shape file for each crop, As a result How can I obtain shape file for any area I like to add crop type calssification?