phyiscal machine (standalone) - for vCentre on 192.168.9.x
Why on earth would you throw a whole physical machine at vCenter? Virtualise it and get yourself another host.
all 3 ESXi are connected to 192.168.9.x but for the UAT the guest OS is supposed to talk to 192.168.11.x
This is a standard VLAN process. You will need a router (this is not VMware's job) on both networks which acts as a gateway between them. As you can configure port groups within VMware for the UAT VLAN.
oh and 1 more, VMKernel and Management should it be of different IP? Because when i gave my management port a different IP (192.168.10.x) it throws a warning citing vSphere HA agent on this host could not reach
I'm not sure what you mean, a management port IS a VMkernel. What you do need is a working isolation address, it looks like your default gateway (which needs to be on that VMKernel IP range) isn't responding to pings.