Hello Sathish
EIGRP uses a TTL of 2 in order to specifically accommodate hub and spoke topologies such as Frame Relay. The TTL will always be set to 2 regardless of the network type you use, and that is why you are seeing a TTL of 2 in your four router Ethernet topology.
Remember, hello messages sent between EIGRP routers are never routed. They communicate only between directly connected EIGRP neighbors. In your topology, each router will generate its own hello packet, thus putting in a TTL of 2.
The only exception however is when you have hub and spoke topology like the one in the lesson. When you send a hello from spoke to spoke, it’s still on the same subnet, but due to the underlying technology, you are obligated to go through the hub router which will decrease the TTL by 1. Thus a TTL of 2 is needed.
I hope this has been helpful!
Laz