Student or Learner
The following sentences come from MACMILLAN, and my questions are in the brackets:
1. It's no use talking to Henry--he wouldn't understand. (Can we use won't instead? Why?)
2. Where would he have hidden the keys? (Is there any difference if we say 'Where did he hide the keys?'?)
3. --Sylvia said it was your fault.
--Well, Sylvia would say that, wouldn't she? (Can we say 'Sylvia will always say that, won't she?' without changing the meaning? When criticizing someone's typical behaviour for a particular action, do we always use 'would' rather than 'will'?)
Thank you very much in advance.