I think you might be misunderstanding what Fiverr is trying to say (though it is a bit ambigous.) The way I always interpreted it is 'if they like you, they will leave a good review=more people might trust you/etc.)
It's not a direct promise to give you higher impressions if the buyer likes you, more of a warning, almost. 'don't mess this up for us'.
Basically, they are just telling you what you already know. If you do well, you have a higher chance of doing well (which, is pretty obvious, right?)
I wouldn't fret much about this and just press on whenever you have a new order.
No - you need to have quite a few orders completed and good stats. Where did you find this information?
If you look at your analytics page, you can find the exact things you need.
(I encourage you to read Fiverr's TOS and FAQ/etc. pages to understand the platform you're hoping to work on.)
katakatica's post in In my recent successful delivery, I haven't got any raise of impression! was marked as the answer
