More details:

Is it possible to say, 'How old's Anna?' Or is it better not to use the contraction 'How old's' and to say it as 'How old is Anna'?

I've also read that it's not a good idea to use the contraction ''s' instead of 'is' in questions if a pronoun goes after it, for example, 'Who is he?' and 'Where is he?' sound better than 'Who's he?' and 'Where's he?' Is that true? :)

Thank you!