20amp circuit with 130 feet 10awg main line and 12awg from junction box to outlets

I’m new here, so I’ll apologize in advance! But I successfully wired up my garage with the helpful information from electricians on job sites and LOTS of research on forums! I had to remove the 20amp breaker that fed 1 outside receptacle at the house from the main service box in order to fit the 100amp breaker feeding the sub panel in the shop. I had enough extra 10-2 direct burial to run from the new sub panel at the shop back to the receptacle at the house so I threw it in the ditch and backfilled it! It is about 150 feet one way.

My main questions/ concerns-
1- Given the distance, could I run the 10awg the first 130 or so feet and then use 12awg in a junction box closer to the receptacle to feed the receptacle for fitment issues?

2- I have an LED flood light on a switch with 12-2 direct burial that I’d like to run on the same circuit. Yay or nay?

3- I won’t be using much from the receptacle at the house and the LED flood light won’t use much current, so I feel like I’m good with the 20 amp circuit, or should I put it on a 15 amp breaker to be safe?

4- What is the best way to splice at a junction box, wire nuts or the screw down type connectors?

Thank you in advance for your help and sorry if I was unclear about anything (A.D.D. is working overtime today! Hahah!)