The minimum that must happen as the result of interrupt.

$1.$ Save the CPU state and call the interrupt service routine, then disable all interrupts.

$2.$ Save minimal information about the interrupt on the stack and enable interrupts $($or at least higher priority ones$),$ then identify cause of interrupt and attend to the underlying request. Daisy chain or Vector interrupt

$3.$ Restore CPU state to what existed before the last interrupt and return from interrupt service routine.

$4.1$ and $3$

$5.2$ and $3$

$6.$ All