Selling car to Cars 24; worried about transfer of RC & Insurance

I am about to sell my own car to the company Cars24 this week. They have a policy of paying on the spot and then either selling it within a few weeks or parking it in their yard until they find an interested buyer. They generally give a sale receipt and delivery note on their letterhead at the time of sale and transaction. Following this route, I understand I may have to chase Cars24 even after they pay me to remind them of RC & Insurance transfer as soon as they sell my car further. My questions: 1)How can I make myself legally secure at the time of selling the car, so that if the car is involved in any mishap, then I am not held legally responsible. 2) What if the new buyer refuses to get it registered on his name after buying it from Cars 24? 4) If my car insurance is expiring in March 2020, should it be renewed if I sell it to Cars24 next week? 5) Is a delivery note on letterhead sufficient or should I get an undertaking from Cars24 on stamp paper with revenue stamp & notorized?