Reliable fair value- Ias 16,38

-if fair value of an asset of a class can’t be measured reliably only that asset shall be measured at cost or whole class of asset?

-if there is NO ACTIVE market for asset (IAS 16,38) ,would it mean that fair value can’t be measured reliably and revaluation model will not be available.?
(in which case IFRS 13’s Level 1 and Level 2’s quoted prices in active market will only be available)