#1: Does your blood contain pure water? No. So you try to keep blood cells in an isotonic medium with your blood. If you put them in pure water they will burst.
#2: It is the similar to the previous question. You put it in water to provide cells gain water. Note that plant cells have cell wall and they do not burst.

Is it clear now?

hypotonic solutions are ones with higher water concentrations, and so when in contact with a cell that has a lesser water conc. then osmosis will occur and water will transfer to the cell and thus how a blood cel explodes from too much or green leaves get plump again as they have water to support thier structure.
Also if your in the swimming pool (the ideal hypotonic solution) then your cells will gain water which is why you go wrinkly after a while, you can also make the connection between the salt or chlorine molecules in the pool as they lessen teh conc. of water by attracting the water molecules and so high chlorine pools means that you wont get as wrinkled as fast.

hypertonic solutions are the opposite they have a smaller conc. of water and so osmosis occurs in the opposite way by the water leaving the cells and shriveling up, particularly plant cells that have a fixed cell wall that wont shrink whilst the middle will which is why the green leaves shrivle in the first place as all the water has left or evaporated ect.. and left the structure of the leaf very weak

hope it helps, and im not sure if i got hyper/hypo round the right way so could some1 check that for me?