Delta Squad is a Commando unit.
Commando Units were clones that got special training to become Commandos as there are made to infultrate enemy line or go on secret missions that involve for example killing a war leader.
The Bad Batch is a clone Unit that is made up of clones that have genetic modification like better vision (hence there called Unit-99 due to clone 99 being a geneticly failed clone).
In no way are they the same as their training was a lot different and have different acces to weapons.
Also no, There not all called Cody as every clone is just a Number like CT-*enter random number*.
The name Cody belongs to a Clone Commander of the 212th Battalion wich is led by General Kenobi.
The Multiplayer has been shutdown as Gamespy decided to pull the plug, but it's still possible to play Multiplayer by either entering a Ip adress (this one 74.91.114.158) in the IP section of Multiplayer or by using a modding tool to enable the serverr browsing.

Hope you found it Helpful.