! sort of
2 not really.
The link from YA is no F****, so it only passes a little authority, not page rank. It does help SEO a little, but not as much as if it were a full blown backlink passing PR..
Becausethe link passes authority, boosting links to it will not really help. It is unlikely that any few links you point to Yahoo will help their authority, (they already have more than most, and the link does not pass page rank). Even if it did help their authority, it s passed down every link in yahoo so it is heavily diluted before it passes thru your link..
Here YA helps you most is with brand awareness and traffic. The traffic is super targeted.
BUT, evry once in a while I see a link from YA that is do-follow. They don't stay that way, but occasionally they pop up that way. I had one for 8 months once