Garden: You need to go to construction mode and there is a section for gardens and you make a greenhouse and fill it with garden soil. Select the soil and it will say "Plant tomatoes" and an amount of simoleons you need to pay in order to plant them.
Fishing: You need to make a pond in the backyard or go to a community lot which has a pond and you select the pond and it will say "Fish".
Hiking: I don't know how to hike. Sorry...
Hope this helps!
