>>73
I think those kinds of questions aren't something you should ask Japanese.
Anyway...

1. You don't have to be nervous. You can't insult others so easyly.
   But you can annoy others easily if you dress like garbage. Seeing backpacker-style foreigners who wear short pants to show ungry hairly legs is really annoying.
2. Don't bow unless you can do it naturally. Just nod like you always do (if you want to).
   Not bowing isn't rude at all.
3. How stupid. Aren't you refering to Korea?
   Freedom of expression is one of the most emphasized ideology for postwar Japanese.
   The Rising Sun flag had never been illegul before, and will never be illegul forever.