Tier 2 visa Extension application when am I allowed to travel?

[Angel89]

Hi all!

Im on a Tier 2 employer sponsored visa and it is due to expire on December 11. Im planning to go home from November 7 to December 2 and decided to apply for sa new visa with a new employer on December 2 once I got back here in the UK. My questions are:

1. Am I allowed to go back without any problems on the UK border with few days remaining on my visa validity?

2. If ever I will get my new COS and plan to apply for a new visa under a new employer before I go home, I plan to pay for Super Priority so I will get a fast decision. Once I get an email confirmation that my application for a new visa has been successful, can I travel even without the new BRP card since my old visa is still valid until December 11?

Thank you so much and I hope you can answer my query!