clamp it on the rosak car chassis instead of the battery terminal

Of course you can. I did several times, jumped to and being jumped. Most important just careful not crossing the terminal polarity only.
Most of 'SOP'/tips for beginner around can safely follow but once you learnt enough they are mostly made up myths so is up to you want follow or not later

proton did release a guideline on how to jumpstart thwir cars. to be safe, better follow the guidelines. cos i dont want to spend unnecessary time and money to fix more problems

Unpainted bare metal connected to the chassis.. not body.. engine block has 1 point..