In the autonomous in Vex u, can you register in both arcs, if you are a blue alliance in the blue arc plus the red one, and diverse with the red alliance?
Could you clarify your question? What do you mean by “register in both arcs”? What is an “arc”?
What do you mean by “arc” and “register”? Neither of these terms is in the game manual. Are you asking if you can score in both goals during autonomous? If so, this question is answered in the manual
I’m wondering if you can score on both goals during the autonomous game in 45 seconds?
Yes, you could score in both goals, but only your alliance triballs. In your example your can score the blue triball in the red goal or the blue goal.
I suggest you to check the game manual. There are some keywoards that could help you to understand all the game.
Read the manual and then read the appendice of VEX U game.
check this link https://vrc-kb.recf.org/hc/en-us/articles/9652912628631-Game-Manual-for-VRC-Teams
Good luck!