You can get this download version just about anywhere including PopCap (more expensive than other sites) or other related sites where its cheaper like Chewy Central (see related link below for the $6.99 and 1 free hour trial deal).
There is a "free" version of Plants Vs Zombies on the PopCap website as well, its a flash version of the game. Its not a full featured as the download version, but still pretty cool (again, see related links below for a link to the game page).
No. If you are referring to the first Plants vs Zombies game, then there's no online full version for that. But you can play Plants vs Zombies Adventures on Facebook for free.
One of the websites or popcap
Yes, there are many places to download Plants vs Zombies from, such as Steam or Direct2Drive.
No or maybe a little bit
No, there isnt.
you can but you just have to look
Forever but falls asleep occasionally
google, plants vs. zombie
Yes. There is a plant VS zombies for the DS. There is also a DSi Ware version on the DSi Shop
yes i have it and i beat the whole game
no you half to download it sorry
in the normal version and the full version its easy u have to plant your plants u have to put lots of sunflowers to get more plants. its easy.