Item rule clarifications

[Nobu]

To be clear on items:

1) You can put as many item cards into play as you want, though only some will actually be used, and the rest are carried?

2) You can put 'use once only' items into play as well, so they are carried, and can be 'used' at any time?

3) Of all your items in play, whether 'used' or 'carried', only 1 can be 'big'?

4) You can only trade items that are in play on the table?