Will i be able to upgrade from ios 9.1 beta to 9.1 stable I upgraded ios to 9.1 beta from 9.0 last beta a week ago. However i can't downgrade it to 9.0 stable as i don't have a backup. 

How will i be able to update to 9.1 stable from 9.1 beta when 9.1 stable released ?

Thanks
Are you saying that your firmware is higher than iOS 9.1 and you want to downgrade back to 9.1? If so, you can't because Apple has stopped signing iOS 9.1 since December, I think. You can learn more from this post.