Hi,
I do not find a form to preview the page to be printed including the crop marks on full screen or still one full screen soft proof of the page including the possibility of two different profiles ICC and not only of each individual image.
There is no feature to see a page "full screen". You need to use the Page Editor screen, accessed by double clicking just outside the page preview or using the icon, second from the right below the page preview. You can soft proof in this screen too. If you wanted to check a different profile for the whole page then you would have to change the profile on the Job Properties tab on the main screen.
You can set set different printer profiles for individual images in the queue. Select and Right click an image on the Page Preview or in the Page Editor and choose Custom Color Mgmt Settings.
To soft proof a single image full screen, hover mouse over the thumbnail and use Ctrl and Space Bar. Alternate use of the space bar will toggle between soft proof view and normal view.
My tests give me crop marks on image margins and not on square paper defined in template.
I think I understand your problem here, if I haven't, please attach a diagram or screen shot to a post.
Yes, crop marks do refer to the image or image plus border and not to the edge of a template.
Do do what you want, make a template that includes a 30cm x 30cm plain white image and add you images to that, on top of the white image.
See attached screen shot which shows the idea with guide lines set which are easier see for the example.
The template would have the square white image with another template on top of it, with a border if required and of the size required. To set up the template on top of the white image, Freehand mode must be used and the page editor used to accurately position the image and template. Save as a Layout and use from Custom sizes.
If I've not understood your requirements or you need clarification, please post again.
Terry