Looks pretty polished already, good job! And sounds interesting. It's a good focus on one thing which is important as differentiator to other social networks. In the past there was Path [1] which allowed only 50 friends, but was more generic. It's also great to go freemium from the start instead of ads or trying to be fully free until you run out of money.

Some questions that I didn't find answered in the FAQ or elsewhere:

- Why does the birth year go into the app settings and not the profile? And 1950 is the default?

- What's the Ferris tag in the app? Like a "secret" identifier? In the settings section maybe this coulb be explained a bit.

- In the app settings notifications are off by default. Is that intended? It's nice as it reduces distraction, but with the interactions on the app being less frequent already (one activity every now and then per friend with just 20 friends) I can imagine notifications being necessary to build traction (not the app itself, but also as a participant, when planning activities, I probably would like my friends to know without them having to actively open the app, especially for spontaneous activities).

- I can only add friends when knowing their Ferris tag. When a friend doesn't use the app yet, I have to explain what it is myself. Maybe you could add an "invite via mail/link" feature, where the friend (not on Ferris yet) sees an explanation what Ferris is, can sign up and then automatically the Ferris friends relationship is established

Good luck with the project!