Depreciation commences when the asset is made available for use and to continue depreciating till derecognition, depreciating even during idle period.
Residual value based on expected future circumstances measured at current prices and no adjustment to be made for changing price.
Depreciation charge is determined separately for each significant part of an item of property, plant and equipment.
Useful life and residual value to be reviewed annually. Changes are considered as change in accounting estimates.