1 - Its more so that you can have an adaptive build. There will be times against certain champions/team compositions where it will be very difficult to survive. So at least building tanky, will provide utility to your team and perhaps even bait enemies into jumping you. These situations will more likely come up if you are very early/first pick in the draft and you get countered by the enemy.

2. In Solo Q, there will be a lot of fighting and kills in any elo you're in. So just getting to your items sooner is much more beneficial. As for the other "hunter" runes, the only other valuable one is Relentless Hunter, to get around on the map faster. For Ultimate Hunter, while Zyra has a good ultimate, she is not really reliant on it to do what she needs to do.

And no problem! If you have any other questions, let me know!. Glad to help. Have a good day