intercorporate investment-differential of reclassification / reversal impairment ifrs & gaap

Anyone can advise if it is necessary to know the different treatment in terms of reclassification & reversal impairment for held for trading, hold to maturity, available for sale? I have hard time to understand it. It is correct to say that: reclassification: Gaap: allow to reclassify ifrs: not allow reclassification for held for trading, allow for available for sale and held to maturity reversal impairment: Gaap: not allow Ifrs: only allow reversal for debt but not equity? Thank you.