How to unlock the wallet?I have only option "Change password"
Go to help, debug window, click console tab, the type ..... walletpassphrase yourpassword 10000 true
the number is how many seconds you wish to keep the wallet unlocked.
This workaround will work until we get a new wallet with a button for it... but until then this process accomplishes the same thing.
Regarding wallet staking, think of having an open wallet with a balance as your miner, the balance is your hashing power. The larger the balance, the more chance your wallet will "stake" and earn a return.