1-Cant I just plug in a Antenna to the router and extend its range.

?
2- Does the DAP-1522 and DAP-1555 have guest networking???
3- And can I remove the Antennas behind the so that i can attach a more powerful antenna??
4- I read a few months back that if u place an external antenna in a good place you can extend your wifi upto two kilometres...Is that true??
Which is better DAP-1555 or DAP-1522??