Where does IP work alone, without TCP?

Question

Computer networks

Where does IP work alone, without TCP?

Answer 1

IP networks are packet switched networks. Therefore, the data path is a rather volatile and ephemeral thing, in the sense that, as a rule, for two addresses (source and destination) there is no "nailed" route, as in the case of, for example, telephony with young ladies (although nuances are possible).
The data path is determined by the behavior of each router (per-hop). Each router receives a packet, examines its destination address (an IPv4/v6 address in this case), and determines, based on the routing table, from which interface this packet should be sent next.
Roughly speaking, it is clear from the routing table which traffic to which host should be allowed through which interface. This resulting path (route) may be asymmetric (traffic from the source to the destination follows a different path than the reverse), may change repeatedly during a communication session.
For more or less intelligible data transfer over IP, transport protocols are used., providing, as a rule, one of the following: multiplexing (see port numbers), duplication protection, protection against distortion of transmitted data, and so on and so forth.

Answer 2

in the same udp

Answer 3

I just don't understand.
It's just a layer 3 protocol, ie. is intended to determine the path of data transmission. How does he do that? In my opinion it only identifies hosts.