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If you're missing two achievements & pick up items, the first missing achievement is either the edelwoods or the rock facts. If it's the edelwoods, make sure you've fully discovered each exterior map (including the first/spawn map!) and inspected each edelwood you find. There will never be more than one edelwood on an exterior map, so if you found one, you can move on. For the rock facts, do the same type of exploration on each exterior map, though there's only 3 so these are less common.
For the last achievement - once you unlocked the 3 act achievements and the 2 item achievements, take a look at the edges of the last exterior map before the end game screen for a secret passage which has been uncovered. Entering the secret room will grant you the last achievement!