I'm affraid the answer is NO. A Bishop cannot become a bishop by the internet. His capabilities, his experience, his preachings, his education, everything is considered when a priest is made a...
Yes if the Bishop commits a sin which warrants his having his authority taken away from him. This has to be done by a higher authority. Usually this is followed be excommunication from the church.
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"Your Excellency" is used when you are addressing the person, like speaking or writing to them. "His Excellency" would be when you are talking to someone else about the person.