Choosing the "Always.. option hasn't been very effective for me even though my settings are default for the Apps in question.
I constantly receive the "Complete action using" window while using stock 4.3 browser with chrome.
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In regards to Question 2)
Audiomanager will give you the option to disable the volume rocker on HTC One.
I understand I'm responding in such a late fashion but with hope someone may find this informative...