1)I can get bitcoins even if my wallet is not on sync? (i doubt that since i dun saw even a micro 
)
)See this:
- http://en.bitcoin.it/wiki/FAQ#What_happens_when_someone_sends_me_a_bitcoin_but_my_computer_is_powered_off.3F
2)Every time i open it , it will need to sync all over again?
Yes, new blocks occur about once every ten minutes, so your client will download any blocks it is missing so that it has all the blocks.
3)How much it have to download? Seems a lot for me and my C partition have not so much space =/
The storage for the blockchain data files is now over a gigabyte and growing. The client allows an alternate data directory to be used (--datadir= https://en.bitcoin.it/wiki/Running_Bitcoin ) if the default storage location (e.g., C: partition on Windows) is not going to be large enough.
Additionally, there are other clients (e.g., Electrum ) which work differently and don't use a full local blockchain.