How to know.. when there are special unit drops...also how to know when we have increased drop rates...are there any atm...

one of my silver is a vampire hunter...can she become my second physical rear...

Are all the rank up bonus for nutaku and dmm same...
i got iris on lv10 and 5 SC on 20...

any special event or giveaways atm..that i should pay attention to...

thanking in advance for the answer..
Kirito Rick