I came to the UK from the United Arab Emirates just a couple of weeks ago. The company in the UK did a CoS letter previously and it helped getting the Tier2 general Visa quickly.
The visa is stamped on my passport that is valid/ allows entry between 17 November and 17 December.
I was advised to collect my biometrics BRP card in London post office. And I did. Now I have the residence permit card. Valid until 2020
Now to the question part:

On the Visa stamp it says I need to register with police within 7 days of arrival. I went to the OVRO and they gave me an appointment to come and register in February!

My question is . Can I leave the UK and re-enter without registering with OVRO ? I plan to travel outside for holidays and meet family members in Europe.
Can I reenter the UK with my residence permit card? Even if the Visa on the my passport says it's valid until 17 December only?
I plan to immigrate to the UK eventually in 5 years time.
I'm confused and no one around me seems to help and police numbers are not being answered.
Please if anyone knows about this let me know
Thanks!