Answer 1

Complete 1 lesson module in any of the tutorials. It can also be a module you have previously completed.

Answer 2

You only need to complete one lesson a day for 15 consecutive days to unlock the badge and to get a certificate. More frequently asked questions can be found here

https://get.sololearn.com/back-to-school/faq

Good luck!

Answer 3

https://code.sololearn.com/WhxS7Gd2NnlF/?ref=app