- what do numbers on the exploration path mean?
- They represent VP tiles you gain at the end of the game, depending where you player marker ends.
- each time an exploration starts, all the explorer should move forward one step on the exploration path?
- The explorer markers only move forward when the exploration cards tell you to do so. So no, no moving forward just because the exploration started.
- it is possible for two player exploring 4 different cards (two each) and then decide to go back to the camp?
Yes, it is possible to explore as many cards as you want. When explloring, each player has to decide on his turn whether to return or keep on exploring. If he chooses to return, other explorer can join him or not, therefore some explorers might explore more cards than others on the same exploration.
- eating is allowed only in the final step of each turn?
Yup. Or unless a card allows you to do so (I ignore it).