Lets say I have one terminal where the output of \"tty\" is \"/dev/pts/2\" From another terminal, I want to send a command to the first terminal and execute it. Using: echo \"ls
No; terminals don't execute commands. They're just channels for data.
You can sort of run a command and attach it to another terminal like this, though:
ls /dev/pts/2 2>/dev/pts/2
It won't behave exactly like you ran it from that terminal, though, as it won't have that device set as its controlling terminal. It's reasonably close, though.