(a) Yes – by doubling all prices and income, assuming one does not suffer from money illusion, individual demand remains the same, because relative prices have not changed.
(b) It is less costly in the long run to change behavior – this includes adaptation to changes in prices and substitution to less costly alternatives. (see also WEW-022)
(c) Cardinal utility refers to a numerical (exact) description of utility. Ordinal utility is a relative ranking. Ordinal says A is preferred to B, but does not indicate the magnitude of that preference.