Multiple questions for 2003 Volvo S80: (1)Ever.

Multiple questions for 2003 Volvo S80: (1)Ever since I synced my visor buttons to my garage door and changed settings on front driver seat positions a chirping/beeping alarm that lasts for approx. Seven beeps has been sounding about three seconds after every time I start the car. Maybe coincidence, but I check fluids and other potential issues and can't find anything? (2)Also, I have changed my taillights, stoplights, brakelights and checked multiple times for faulty lights and all are working properly but I still get a message everytime I press the brakes "check stop lamp"? All lights work. (3)Next question.I continue to get message "time for regular service" every time I start car. I have had "regular" maintainence done, i.E, oil changes/fluid checks etc. But message remains, (4) check engine light stays on all the time despite not having any outward signs of problems, (5) last question I can think of right now. The radio has been changing stations and its "source" (am/fm/cd/tape) all by itself--this problem started when weather began to get cold? Thanks for all your help! Michael