Boot form external drive question

[Gpl]

Hello,

i have an imac 2012, i have made some upgrade and broken a capacitor so i'm waiting for the new capacitor to reassemble the mac.
Now my question is, can i use the imac 2012 hdd as external drive an boot from it, with an iMac 27 without compromising files ?

Thanks

 

[Fishrrman]

This will work but only if the older drive has a copy of the OS on it that is capable of booting the different iMac...

 

[Gpl]

both are high sierra
the problem is using external on differnt hardware did't mess nothing ? (Like windows

 

[Gpl]

It works in the 27, i will give update if it will ok when i will reinsert in the 21