Answer 1

There is no opition to reset or clear progress currently.. option removed.
But You can revise any number of times, from start..

Answer 2

https://www.sololearn.com/discuss/3013944/?ref=app
https://www.sololearn.com/discuss/3042745/?ref=app

Answer 3

You could start from the begining, but youd need to create a new account if you really want to reset your progress