Microsoft simply abandon us ( old Lumia users with 512 MB RAM) . With this selective update process MS able to get rid of all old Lumias specifically Lumia 520s & Lumia 630s which make the large chunk of their active user base.
Updated my Lumia 535 8.1 version to windows 10. Fantastic version!!!!!! Looks awesome.....
Time taken- 1.30hours, data-500mb
I most like the default browser Microsoft Edge, it is better than anything.