front row
 

When can/can't a front row player return a serve?

The restriction is that the receiving time may not block a serve, not that the front line cannot return a serve.

So turning to the definition of a block. The player is: 1) close to the net, and 2) is reaching higher than the top of the net.

They also can't complete an attack of a serve that is contacted entirely above the net. USAV/NCAAW have this restriction only if contacted in the attack zone, whereas I don't think NFHS has that caveat.