1. You can't do anything with intel until you have contact.
2. One CI can block multiple intel attacks. I normally run just one and with my intel intensive race can then block all the incoming and use the other 11 slots to crush their own CI.
3. I am very sure that I have PPPed the Terrans homeworld before. I had 11 PPP's hitting them per turn as a MEE since they were weak and the Krill were rapidly becoming a second MEE and a threat on the far side of the Galaxy... Next thing I know is I have world with Large size (as all homeworlds that game were) with the 120ish % in all resources that homeworlds of good value have, and mineral miners, 1 organic and 1 radioactive, with a resupply a spaceport a spaceyard and the rest filled with research. To top it off the Weapon platforms on it where like an evolutionary chart of the Terrans advancing techs. 1 with CM 2, 1 with CM 3, 1 with CM 4, then a whole lot with maxed CM all using the graphics of the Terrans.
I thus conclude that PPP is possible of homeworlds. Heh... too bad I don't still have the game and don't remember if it's type said homeworld. I mostly ignore those planet types thingies and most of mine are just blank or have something generic like resource colony, or R&I colony.