Anyone has "admin" powers over bitcoin network?

[Tungsten]

I wonder if Bitcoin was "launched" and now operating fully according to algorithms or someone can still "tweak" things, like hash difficulty etc... ?

[colindean]

It's all in the algorithms, now. A change in a client produces a different output than the other clients expect, causing that changed data to be invalidated by other clients in the network.

[CIYAM]

Bitcoin is a P2P protocol written into open source software so there is no "admin" in the sense you are thinking of and any changes that you want to make to your copy of the source code (such as the block reward, difficulty adjustment or any other rule) that are incompatible with the rest of the network would simply result in you building a client that no longer co-operates with the network (i.e. is useless).

[FreeMoney]

There are no special admins. The only code that runs bitcoins is the code you can run yourself. You and anyone else can change anything you want in that code and all that will happen is that you'll be ignored by the people who didn't make a similar change.