So, I don't have to do anything in the bios, when I put it in the 6 Gb/s connector.
It will automatically find the SSD as a boot drive and the speed of 6 Gb/s.
Yes, it will find it.
Another question could I change it from IDE mode to AHCI mode without reinstalling OS?
That is possible too.
To fix that, enable the AHCI driver in the registry before you change the SATA mode of the boot drive. Follow these steps:
Exit all Windows-based programs.
Click Start, type regedit in the Start Search box, and then press ENTER.
If you receive the User Account Control dialog box, click Continue.
Locate and then click the following registry subkey:
In the right pane, right-click Start in the Name column, and then click Modify.
In the Value data box, type 0, and then click OK.
On the File menu, click Exit to close Registry Editor.