2 question please. Can I have two or more unique attachments or lands in play? Can I play unique attachment or land, if I have the same card in discard pile?

You can have all unique attachments and/or location that you want into play, as long as they have different names: for example you can have in play Aegon's Blade and Lady Daenerys Chamber, or Khal Drogo's Tent and Aegon's Hill at the same time.

The important, for unique cards, is the DEAD PILE not the discard pile. So a ICE (unique Stark attachment) in the discard pile doesn't stop you from playing another ICE you have in your hand on a Stark Character.

In the case that you have in hand the same unique card you have already in play, you can attach it for free (unless it's a Shadow card...) as a duplicate of that card in play (in order to save it), but you can't play it if that card is in the dead pile.