Mac Hard Drives not mounting

I have a apple mac air laptop and i used to have mountain lion OS and i just downloaded the newer sierra OS which i don’t like and i tried to factory reinstall the OS back to mountain lion,and apple said my internet speed isn’t strong enough to for me to do it as i tried and it keeps falling and i they said to bring it in.Could you do it and how much will it cost and could it be done while i waited?.

External Hard drive stop working after I plug the wrong adapter. The drive is not spinning and is making no noise. I tried another external hard drive interface, hoping the USD/SATA interface of the external hard drive was to blamed, but no luck.

Disk can’t mount (MacOS 10.12.4)
Running Disk Utility:
Catalog File shows an incorrect Block Count for file tmp.spotlight.state
The disk can’t be repaired
Disk: WD MyPassportStudio 2TB Firewire & USB version

I own a 1TB external USB hard drive from Western digital, which has failed recently. After connecting it into the computer, it keeps spinning without getting recognized as a USB Mass storage device on the computer. I was lucky to have the drive detected just once, where it sent me an error message regarding an error with the i/o device and denied me an access to the contents. Having experienced this issue after multiple attempts, I believe a data recovery might be required. Can you please assist me with the same ?

new macIt is a 2009 iMac – the hardrive has now failed (due to age and use). Apple have confirmed this.
We have photo’s and possibly music/films we would love to recover if this is possible?
It would be great to know a cost for this also.

I deleted a folder from my back up drive into recycle bin, then emptied recycle bin.
I’d like to recover folder

Laptop not powering up, had had problems with not charging for a few weeks. Removed HDD (wd500LPVX) and put it in an external enclosure which I know works. It is not recognised by two separate PCs. The disc spins but does not click, looking at it with disk managment software it says it is a GDT disc. Can you recover the data for me?

External hard drive dropped, has been clicking when staring up two basic computer shops said can’t fix it, have opens it up and the bottom head is damaged.
It is a western digital hard drive, 2tb but was only about 1/4 full of photos etc, will you be able to recover the data and if so what would be the rough cost?