how to transfer low resolution photos ( optimised ) to the computer I deleted all my pics from iCloud and also the recently deleted items in order to reduce the space and revert to the free version ( 5 GB ). 

I did check all the pics before I deleted them from iCloud if they existed on my iPhone. Now, the thing is that all the pics that I deleted from iCloud were infact stored as low resolution on my iPhone. So, the device shows all the pics, but they are all low resolution. Ofcourse the high resolution that was stored on iCloud is deleted directly from iCloud and even the Recently Deleted items.

So, what is the solution now? I am happy with the low resolution pics as well. Ofcourse, if I could retrieve the high resolution pics, that would be the best solution.

Looking for help.

EDIT to clarify the question -

I can see the low resolution pictures on my phone, because I restored the low resolution pics from a iTunes Backup and as soon as the restore was successful, I disconnected the internet to avoid syncing with iCloud. Now, I can see all the low resolution pics on the iPhone, and the question is how to bring them on to the computer. A definite solution is to use commercial tools such as EaseUS Recovery tool to extract the iTunes Backup, but that just costs money. So, I am here to ask for other solutions that doesnt cost money. 

In other words, the low resolution pics ( I really dont care about the high resolution pics anymore ) on my phone has to be transferred somewhere - maybe using AirDrop or Bluetooth..without connecting to internet to avoid syncing with icloud.  Is that possible?
If you deleted the photos from iCloud directly more than 30 days ago, and it appears you did if they're not in the Recently Deleted folder, then they're probably gone for good.

iCloud is a syncing solution and not a backup solution.  It doesn't store a copy of the pictures, in the way that using something like Dropbox does, it give you access to the pictures on all your devices.  At some point, you selected Optimize iPhone Storage in your iCloud settings.  Doing this only stores low-res versions of the photos on your device while the full, high-res photos are stored in iCloud.

If you saved any of those photos from iCloud directly to a computer, that would be your only remaining option to get the high-res versions.