I endountered a web site that to view a video required downloading Chrome but after installation and restart Edge diappeared and the Windows 10 start in the lower left hand corenr no longer worked.  What ahppend and how do I reover Edge and start options?

1.If you have not downloaded the following update for Windows 10 then download and install it.

Cumulative Update for Windows 10: August 5, 2015

2. Open a powershell administrator command line and run this command:

Get-AppXPackage | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register $($_.InstallLocation)\AppXManifest.xml}

3. Creating a New User Account.

4.Using DISM Command:

I) Press Windows + x on your keyboard.

ii) Select Command prompt (Admin) to open Administrator Command Prompt .

iii) In the Administrator: Command Prompt window, type the following commands. Press the Enter key after each command:
     dism.exe /online /cleanup-image /scanhealth
     dism.exe /online /cleanup-image /restorehealth

5. Using sfc /scannow

a. Click on Start button and type cmd in search box.

b. Right-click on Command Prompt and select Run as administrator.

c. Type the following command and hit Enter.

sfc /scannow

 What ahppend and how do I reover Edge and start options?

Have you tried uninstalling Chrome?  Did Chrome try to make itself the default browser (with or without your consent)?  Then that could be analogous to the situation in W8 where IE must be the default browser in order to have access to the Immersive browser (aka MUF IE).  You can have more than one browser without declaring a new one to be the default browser.  Alternatively, you could try seeing what happens by making IE the default browser.  E.g. in an Administrator Command Prompt enter  computerdefaults.exe  Then click Custom and choose Internet Explorer and OK to initialize it.

Good luck