Few questions about Madrid.

Just finished a 5 day holiday and it was great, first time in Madrid but have been in the south of Spain many times. What's with the different branches of police, municipal, local, nacional and Guardia civil. I seen municipal, local and nacional on the streets at the same time, often at the same place. What's the difference between them all?

Do Spanish people not have milk in their tea?

Why are homeless people so "in your face" about giving them money?