Beginners questions: PayPal, Upgrade, Backup

RouterOS Beginner Basics
1

I’m new at this because a friend of mine died and his family has asked me to take over his public hotspot:

  1. I’ve tried to add http://www.paypal.com at walled garden, but it does not work. For the beginning I would issue the codes manually.

  2. Is there a way to automatically do this? User pays through PayPal and the usermanager automatically ad that user.

  3. We’re running vers. 3.13. What’s the newest one and is there an easy way to upgrade? eg. save the configuration, upgrade, load saved configuration. If this fails is there a way to simply turn it back to 3.13.?