Multiple field, but each one as individule I need an image field with only 2 field limit.
I need to call first one front and second one back and be separated.(no problem I can do that with hook_form_alter)

My problem is that in drupal 7, in adding the content, it doesn't show the second field upload button until you upload the first one. 
You have to add the first file, than click on "add another" to be able to upload second file and after uploading both if you delete the first one, the second one goes to first one place, which I don't want that to happen! 

I know I can make two separate fields call one front image and one back, but I want to know if there is an approach to do this with only one field. (save a database table)

Thank You
Just use the single image field, add field description text for the user in regards to clicking to "add another" item when uploading the two images.

On updating, the user can adjust the weight of the images and drag/drop the front/back images into order.

Alternatively, you could look at using two fields, or a module like field_collection