decimation filter delay

Hi members
I am new to multirate dsp ,I understand that to down sample you need to
have antialias filter bandlimited to Fs/2(Fs output sampling rate)and take
the M (decimation factor)samples and discard M-1 samples. My questions are

1)Is antialias filter itself called decimation filter 
2) delay in FIR filter is given as (N-1)/2 (N. no of taps) ,what is the
formula if I decimate by factor M, and Is this formula is applicable to all
kinds of FIR filter (I mean symmetric,antisymmetric ,linear phase etc)

3) If I decimate by two stages by M1,M2 factors ,How to calculate FIR
Filter delay 

Thanks in advance 

Regards
klus