According to what I know, the first beat has an accent on it.
What if the score indicates explicitly an accent? Is that note supposed to be much more accentuated than usual?
Yes, you should bring out that note if it's explicitly accentuated. But not always much more. It depends on the piece and the phrase. There is always nuance. I cannot describe this in text. You need to listen to good recordings, listen to master classes to build a good taste.
Yes, we normally know where 'one' is by it getting a little extra stress. Lots of exceptions though The 'back-beat' in much popular music stresses beats 2 and 4. Reggae stresses beat 3.
Yes, an accent means 'give it a bit more than it would have got'. All in context.