You haven't studied the matter. There are secondary sanctions in place. Unless there is something really important (like oil), China isn't willing to breach these sanctions
No.
A deal need to made for serious Chinese investment to happen in Iran
I agree, but in geopolitics there is no fair or unfair. It all depends on who is more powerful and who has more interests in a deal happening. Complex matters
Just to make it clear, China even followed a lot of the 2014 sanctions imposed on Russia. Does anyone here really thinks that current Iran is more important to China than Russia?
IMO the only way I see China breaching such sanctions is if they to fully sanction Russia in a potential Ukraine invasion scenario. And even there, I think that China would only selectively break the sanctions
Agree with your assessment. China had to follow the 2014 sanctions on Russia and more recent Iran ones during Trump's "maximum pressure" campaign as good faith to the US to prevent sanctioning of SMIC, COMAC, DJI... by kowtowing to US demand. However, these players are now all sanctioned, and the US has already played its hand. While the US could always ramp up more sanctions, they don't matter to china as much.
Every time the US sanctions you, they inflict pain but also there is a corresponding reduction in the threat of future pain. I'm sure the US would want to sanction Lenovo/Haier, but that is one where they would inflict less damage on China than potentially itself. China could go for the jugular and sanction Boeing as well as preventing use of chinese air space in coordination with Russia.
China will have to break multiple sanctions if Russia were going to be sanctioned by the west. Russia basically relies on China for consumer goods (not hard tech), and American "mother of all sanctions" are designed to target the civilian market. Make no mistake, sanctions on Russia does not involve America or Europe restricting trade with Russia, its ALL about driving trade away from China. Its like how US sanctions on chinese semi conductors increased demand for US chips (qualcomm) by china in short term.