Ofcourse not, its only frowned upon if you do it as your teams going through a rough patch and you abandon them for a highly successful team. Supporting multiple teams is fine, just as long as the above isnt the circumstances you won't be frowned upon.

Yes unless your parents or something come from another country or maybe you've lived there

Yes! You should have passion for your national team. Admiring other teams quality is absolutely fine though.

Yes. You should be kneecapped, hung, drawn and quartered in front of her majesty for high treason...

Yes. I can understand if you have another country you like to see do well but your country is your country.

It's not 'wrong' you can live your life how you want too, but some people may find it disloyal. Your country has given so much to you so maybe you should give something back and support the side

no just its usually unpopular in that country

Nope, it doesn't matter, it is just a team. Your friends may get mad at you for not supporting your country, but it doesnt matter

I don't think so the sport wins!

Never.... It depends on u only...