Act Two, Scene One Questions

This scene opens with the words ‘Mislike me not for my complexion’ Why does the Prince think Portia will have a problem with the colour of his skin? Because he thinks that her father wont accept her so hes scared

.What must Portia’s suitors give up if they try and fail to win her? 
‘You must take your chance, and either not attempt to choose at all, or swear before you choose, if you choose wrong never to speak to a lady afterward in way of marriage’

Portia tells the Prince of Morocco- ‘Yourself, renowned prince, then stood as fair as any comer I have looked on yet for my affection’ What does this mean? (if you’re unsure check sparknotes translation