google it. There are some great comparisons.i2p = Garlic Routing (kovri too)tor = Onion RoutingFreenet = I don't fuck with it. I understand you donate some hard drive space to the network. also, really bad shit that I don't want to fuck with there. (I used an i2p > freenet gateway just out of curiosity)
I know but I won't tell you unless you pay me in BTC.
all are their own entity but similar in function. in layman terms these are like different layers of the net.