since it's the solemnity of the annunciation, can we eat meat today? can we also do the thing we gave up for Lent since it's a solemnity (like we can on Sundays)?
1. Yes, since the law of abstinence and fasting does not oblige us on Solemnities
2. "The thing we gave up" is a matter of personal practice, so it is up to the individual, perhaps with the advisement of his spiritual director. It used to be that we were required to fast Monday-Saturday during Lent, and abstain from meat on every day including Sunday. While that has long been removed from the law of the Church (meat on Sundays has been allowed for a long time, and the literal 40 days of fasting [6 weeks with 6 days, plus Ash Wednesday and the 3 days after it=40] has been no longer required since 1966), I think it offers a good practical guide. Sundays, and now Solemnities, less the penitential nature but our feasting, as it were, should still be tempered in light of the season. In Milan they wear black on weekdays of Lent and violet on Sundays to mark this. So, personally, I think some aspect should be kept up
Of course it depends on the nature of your penance as well. I have been observing the traditional fast and abstinence (as recommended, but not required, by the bishops), so I will still give up meat on the Annunciation and Sundays, but I won't fast. If one gave up drinking alcohol, for instance, it may be good at least to keep it to one drink or something of that sort. But as I said, there is no law that regulates this.