Can I use current Bitcoin protocol and Bitcoin client to create my own controlled currency? Since Bitcoin network and Bitcoin currency are not so reliable and can't be controlled.
Also, they are open source. How difficult it is to use the current client and protocol to create a new, independent currency controlled by me?

I will use such currency as a medium for money transfer. Much like a website money or credit.
If I used the current Bitcoin as it is, I would be responsible for all Bitcoins in the world. I want to be responsible for the Bitcoins created by me only. So even if the project will end or the value of Bitcoins goes down, I can then compensate my clients for their loss.

What experience and knowledge needed to accomplish this?(Hardware and Software).
Bitcoin is a decentralised cryptocurrency, meaning there is no central authority to control it. What you need to look into are centralized currencies. If you want to go for the easiest route, all you need is knowledge of programming websites and databases and you can easily make some database storing arbitrary numbers representing an amount of your currency belonging to someone. This, however, would be like Facebook credits, Microsoft Points or the like, not really a cryptocurrency. You could look into centralised cryptocurrencies, like loom.cc . Also worth noting are Open Transactions.

One could, however, create an alternative decentralised cryptocurrency, like SolidCoin, LiteCoin and dozen of others, but that doesn't create as much solutions as it causes problems. If you'd modify the source code you could make it so that only one address is allowed to create coins, but the whole system would be vulnerable to numerous attacks as your computing power might not be enough to secure the system.

All in all, it is not hard to create a centralised currency, but Bitcoin model might not be the best to use for this problem.