Connect two local networks
First, you should disable NAT on you Wifi Access Point. I am not sure if this is possible with NetGear's stock firmware.
Second: clients 1 and 2 don't know the route to the 192.168.2.0/24 network, so they send everything to their default gateway (192.168.1.1). If you add a static route to 192.168.2.0/24 on the modem, everything should work.
Remark: Clients A and B don't know the route to 192.168.1.0/24 either, but their default gateway (the WiFi AP) does.