Wait until i tell yall about SAE-ISO protocols. To use some of the more in depth protocols to talk with ECUs you're only options _through official SAE channels_ is to become a "partner" register for classes during a select time, and purchase class materials such as the protocol documentation, take the class (if there even is an online class) then, possibly you may know how to interact with a particular protocol without reverse engineering it. Hint, if you're smart enough, it's far cheaper to packet sniff and attempt to reconstruct. The issue is it's not repeatable across mfgs and vehicles. You also need to have a business TIN registered and I think becoming a partner required a donation of like $5k.

Finally, it's often against copyright protection to use this knowledge on a real vehicle, such as flashing firmware or entering boot-mode.