Twinkling scene

Is it a good idea to use the IM&LC prepass files when rendering final image with much higher resolution?

Yes it's a good idea, but for lightcache only.
Irradiance map is resolution dependant, so you need to adjust (min and max) for the desired resolution first.

Is there the way to make IM&LC prepass each N frame?

Yes sure ! The FlyWizard do that.

How to exclude the object from GI?

SolidRocks don't manage this. it's vray related.
right click on object-->Vray properties.