The method is far more complicated than i thought and it uses various things that i never heard previously (such as Feldman’s verifiable protocol). Additionally there are many things that i couldn't understand such as
1.They convert the(2, 3)-threshold shares xi of x into(2, 2)-threshold shares wi of x with appropriate Lagrangian coefficients
I don't say it's bad method (rather i find it interesting), but it's very complex while involving third party (Service Provider and Recovery Server in this case).It's definitely not for people like me.