Dua after Salaah

Q: In Bahishti Zewar it states:

6. On completing the salaat, both the hands should be raised up to the chest and dua to Allah Ta'ala should be made for oneself. And if he is an imam, he should make dua for all those following him as well. On completing the dua, both hands should be passed over the face. The muqtadis could make their individual duas or, if they can hear the dua of the imam, they could say aameen to it.

Coming late for Taraweeh

Q: When I reached masjid for tarawih, four rakath already finished, then I prayed first four rakath Isha and started for tarawih. When I started to pray for tarawih seven rakath is going on, after finishing tarawih by imam, still I need perform 6 rakath tarawih. In this situation what I need to do, whether I need to pray witr salaa to follow by imam with jamat first and then need to perform balance six rakath tarawih, or first I need to perform balance six rakath tarawih and perform witr salaah alone?

Laylat ul qadr and taqdeer

Q: What's the link between laylat ul qadr and our taqdeer? i.e.: on the one hand, the pen's ink is already dried, and on the other hand, laylat ul qadr means the night of destiny. So would that mean that each year when laylat ul qadr happens, Allah can change our taqdeer?