Unable to open Anki

I just recently downloaded Anki and have been playing around with the system trying to create an “extra” field in the cloze card to mimic the layout I am seeing in many Anki tutorials. Unfortunately, I must have messed the system up and this window below pops up when I try to open Anki. I tried to delete anki and start afresh, but that didn’t work. Is there any way I could start from default again?

Anki was unable to open your collection file. If problems persist after restarting your computer, please use the Open Backup button in the profile manager.

Debug info:
Traceback (most recent call last):
File “aqt/main.py”, line 441, in loadCollection
File “aqt/main.py”, line 462, in _loadCollection
File “anki/storage.py”, line 59, in Collection
File “anki/collection.py”, line 101, in init
File “anki/collection.py”, line 196, in load
File “json/init.py”, line 357, in loads
File “json/decoder.py”, line 337, in decode
File “json/decoder.py”, line 355, in raw_decode
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

you have installed an older version of anki while your collection is for a newer version.
install the previous version of anki that you had from here (you can install the latest beta/alpha version if you don’t know which version you had installed from here )
when you installed the latest version, go to “File -> Switch profile” and press “Downgrade and quit” then install the version that you want to use.
it should solve the problem