Helen, regarding your many itinerary requests for this trip, those are very personal choices. Travelers should choose what to see and what to do based on their own individual interests and not someone else's, that's why there have been many prior recommendations in your previous posts to make good use of a guidebook.
With day trips and short stays, you also need to plan around specific dates sometimes: not everything is open every day, and things like "free" days at big attractions can throw a wrench in the machinery as they're usually to be avoided on those days due to huge crowds and long lines. Some big attractions also require advance bookings to work around long ticket queues. Weather? Yep, that can throw another wrench in a 1-night or day-trip plan: the CT or Bellagio wouldn't be fun in pouring rain.
Over 6 months of posts, all we've been able to gather from your interests - and only if digging into those threads - is that you don't really like museums and appear to be focused on shopping...which is something very few of us go to Europe to do or wish to trade sightseeing time for with short location stays/visits. There's also only so much room in the suitcase for a lot of that and/or weight we're willing to haul on and off trains and up/down hotel stairways! 😉
Anyway, those many recommendations for using a guidebook are not to blow off your questions but to very kindly help you choose what to do with the amount of time you have and your personal interests plus stuff like how to get around. It can be one of the best resources you can have both before and during your trip.
If not arriving until early afternoon, you won't have a lot of time for the lake area, and daylight will be relatively short. The best you could do is grab a boat shuttle to Bellagio and explore on foot for a few hours, weather being favorable. There isn't really a lot to do there but your guidebook and the tourism website below should be helpful. Do the same in Varenna (tourism website link also below) the next day before grabbing your luggage from the hotel and heading to the train.
https://www.bellagiolakecomo.com/en/bellagio-lake-como-italy/POI-points-of-interest/tourist-information-office
http://www.varennaitaly.com/en/
Enjoy your trip!