If I give a resource to an opponent for free, do I offer it to him openly or in a concealed fashion?

Frenemies

You offer the resource openly, e.g. by saying, “I'd like to give you one grain. Do you want to accept it?”

If I receive a favor token, do I have to place it face up or face down in front of me?

Frenemies

If you receive a favor token, you place it face down in front of you. However, you may view your favor tokens at any time to check which ones you have.

May I use a Monopoly to reclaim a resource I have given away?

Frenemies

Yes, although that wouldn't be a very friendly action.

On my turn, am I allowed to immediately use a favor token that I received due to an opponent's road building action during the preceding turn?

Frenemies

Yes. The only favor tokens you may not use immediately are those you have received by means of your own actions during your turn.

The German game rules state that a player may use or exchange favor tokens only once per turn, while the English rules do not include this restriction. What is correct?

Frenemies

Favor tokens may only be used or exchanged once per turn.