Is there a yellow fever vaccine shortage?

When not given on the same day, is the interval between yellow fever and MMR vaccines 4 weeks (28 days) or 30 days? I have seen the yellow fever and live virus vaccine recommendations published both ways.

I have read that Dengvaxia is built on a “yellow fever vaccine backbone.” Does that mean it can also protect against yellow fever?

Which vaccines can be given to people who are breastfeeding?