Yes - The rule is that you can do 0, 1, or 2 actions on your turn in any combination or permutation of DRAW, SHOP, PLAY, or CACHE (After taking your mandatory draw, of course). A few examples of an acceptable turn: 

1. 1) Mandatory Draw, Elective Draw, Elective Draw (Drawing 3 total cards!)

2. 2) Mandatory Draw, Elective Shopping, Elective Play Action Card (+Bonus Character action)

3. 3) Mandatory Draw, Cache Action (Here, the player skipped their second elective action)

...the possibilities are quite numerous! 

Candidly, that player will probably not win. Frankly, the Apocalypse doesn't care about your feelings.

On the bright side, that is pretty unlikely, so you and your friends will have a great story to reminisce about!

Indeed! In the case where the MAD ORACLE has been revealed and a player is instructed to "draw from The top # cards in the draw pile", they may take any of the top # cards that are not the MAD ORACLE. 

For example, the seer's character card ability instructs them to "Look at the top 3 draw pile cards. Place 1 in your hand." Let's say that the MAD ORACLE has been revealed. In this case, the player still picks the top three cards - one is (of course) the MAD ORACLE, another is BOX OF AMMO, and the third is PREMONITION. The player may take BOX OR AMMO or PREMONITION into their hand, but NOT the MAD ORACLE. Afterward, the MAD ORACLE is replaced on the top of the draw pile, with the untaken card beneath it.