1. Can I create and add my own version of an emotion with an icon?
Yes, you can add new custom Actions within CB Activity > Actions.
2. Where to translate into this:
Normally there are no default filters. Those were added by CB Quickstart. So you should have language strings for them that you can translate using language overrides shown below.
www.joomlapolis.com/blog/kyle/18701-language-overrides-have-arrived
There's a built in search feature that should help you find those language strings, but their language keys are as follows.
PROFILE_ACTIVITY_FILTER_CONN
PROFILE_ACTIVITY_FILTER_GALLERIES
PROFILE_ACTIVITY_FILTER_GROUPS
PROFILE_ACTIVITY_FILTER_FOLLOWING