My wallet is version 0.8.6 beta.
Can I continue to use it?
yes
If I upgrade to 0.9.1 version I have to download all blockchain?
no
I just upgraded to 0.91 since I was using 0.9. I've never input my password using 0.9 but I have with prior versions, is there any reason for me to start a new wallet and transfer funds? As I understand, my bitcoin wallet password should be secure if I haven't entered the password into the 0.9 client?
no, no reason to do that