If I decided to save bitcoins in bank, how will deposit rate be changed compared to dollar or other currencies? Will it have much lower percent?
If you mean for this time then there is no bank that would offer a service similar to this what you are asking.
A strong reason behind using bitcoin is to avoid banks and be your own bank by managing fully your own bitcoins.
Yes and if bitcoin has own bank, bitcoin will not be decentralized anymore.
Better just manually calculate the percentage of your bitcoin to know whether it accumulate some profit. Or if you really want to use bank, you can deposit your bitcoin to there but it will turn to fiat. So its good to hodl your btc.