I have a UK Biometric Residence Permit under Tier 2 and I want to visit Jersey (not NEW JERSEY, the Jersey between England And France, a tiny island) for a sport event. I am not sure if I will be able to enter and exit Jersey without any additional visa. Does Jersey come under the UK of Great Britain and Northern Ireland?
Jersey and Guernsey require a valid visa or visa exemption to enter the UK, no more, no less. So if you have a residence permit that allows you to enter the UK, you're good for short stays in Jersey and Guernsey as well (up to 6 months, which also count against your UK time limit as well if applicable). There are no immigration controls between the UK and the Channel Islands.