What was the answer 'this is second to "Eretz", and this is fifth to "Eretz"'?

Rashi: The verse repeats "Eretz" to make olives and dates (written after it) more esteemed than figs and pomegranates. Pomegranates are the fifth species after the first "Eretz"; dates are the second after the latter "Eretz".

Maharsha: Rashi mentioned figs for a Chidush - olives and dates are more esteemed even than figs, which are fourth from Eretz. Why did he not teach a bigger Chidush - they are more esteemed even than grapes, which are third from Eretz?

Tosfos: If one has wheat and olives (each is right after Eretz), or barley and dates (each is second from Eretz), the one earlier in the verse (after the first Eretz) has precedence for Berachah.

What do we say about one who blessed not according to the proper order?

Mishbetzos Zahav (OC 168:1): He is called one who transgressed Torah. Perhaps he is excommunicated and lashed mid'Rabanan. This is unlike attributes such as Shalem, clean and big, which are mere precedences; they are not based on letter of the law. Chashukei Chemed - if one blessed unlike the Torah's order, perhaps one may not answer Amen to it, just like we do not answer Amen to one who blessed an unnecessary Berachah (215:4). (NOTE: It seems that these are different. There, the Berachah was l'Vatalah. Here it was not. Further, the person can decide not to eat the other species, and it turns out that he blessed properly! - PF)

Why was Rav Chisda so excited about Rav Hamnuna's answer?

Ha'Boneh: It was difficult to him - why was Eretz repeated? Now he knew - to give precedence to the species written after it.

Why did the Torah need to write a second Eretz? It could have listed the seven species in their order of priority - wheat, olives, barley, dates, grapes, figs and pomegranates!

Etz Yosef citing Semichus Zekenim: The Torah did not want to put tree fruits (olives) between Pri ha'Adamah (wheat and barley).