Hallo.

the Recovery Mode is triggered after Windows fails to Boot for the 3rd Time in a Row. turn on the Laptop and hold the Power On Button until it shuts down. repeat the Procedure two Times more. next Time it should Boot into Advanced Start Up Mode. but sometimes you can Boot into Advanced Start Up Mode by pressing F8 or Shift + F8 during Boot.

is your Hard Disk encrypted? because actually you should be able to access the Data via USB Cable. even if the Boot Partition is bad you should see some NTFS and not RAW Partitions.

try to install Windows 10 from Scratch. use MS Media creation Tool and create a USB Device or DVD. Dells ISO Files are basically the same.

Download Windows 10 

delete all Partitions during Windows Installation and then click "New". it will create all needed Partitions automatically.

Sounds like drive is slowly failing (that should not have happened unless it was dropped or something). I would test it carefully before re-using (with SMART enabled software).  I use Crystal DiskInfo and Passmark DiskCheckup.

SSDs are cheap these days. 256gb should be fine for Windows, all apps, and even a few large games.

The BCD may be damaged.

You can try to unlock:

Boot from the win 10 DVD

Launch a command prompt Run several bootrec commands:

Bootrec /fixMBR

bootrec /fixBoot

bootrec /rebuildBCD

Drive is locked could also mean there is a bios password on it.

System prompts for a Hard Drive or BIOS password | Dell US 

Changing to a new drive will not recover from this. It will lock the brand new hard drive.

Contact Dell for Password release code

On contacting Dell Support you will be asked to confirm the below for security reasons:

• Ownership of the computer.
• Whether you are authorized to clear the password on the system.
• Contact Information.

Please have the full error message along with your system Service Tag information as this is required to create the release code.