Normally, the tzibbur should daaven Mincha silently and then the chazzan should repeat the entire Shemoneh Esray. If there is no time, our minhag is to have the chazzan begin out loud the first 3 berachos so everyone can answer Kedusha. When he finishes Hokayl Hakadosh, the tzibbur will begin their silent Shemoneh Esray. (ShA1 – MB1 – BeH “hash’liach”)
In this shortened tefilla, the chazzan’s Shemoneh Esray is just as the other individuals, therefore if it is a fast day he will not say Anaynu as a separate beracha – rather he will insert it into Sh’ma Kolaynu. (BeH “hash’liach”)
If you usually daaven Mincha b’tzibbur at shul, you are allowed to have a sit-down meal any time before then. Certainly snacking is allowed. (Rama2 – ShA3 – MB26,28 – see ShaH 235:19)
Once it is noon (a half hour before Mincha Gedola) you should not begin a big banquet before daavening Mincha. Since it is common to become intoxicated, we are worried that you will miss daavening Mincha. Banquets are held for weddings, bris mila, pidyon ha’ben and the like where there are many people eating together. (Rama2 – MB24, 30)