Travelling to Italy & Switzerland for 14 Days (help)

Are you departing by air on December 5? From what airport?

I strongly recommend you invest in one or two good tour guidebooks such as the RS guides sold on this site (and no, I'm not affiliated with the Rick Steves organization in any way). Compared to the money you're spending to get to Europe, the cost of a couple of books is negligible and those books will give you tons more information than you'd ever be able to get from posting such a general question here.

That said, I'll try to give you a few basic answers. Cinque Terre in the winter may not be very enjoyable, and the weather may even preclude your ability to get there (or back), so I would forgo that. You would have enough time November 28-December 4 to travel to Lake Como and the alps. Here is a RS video about that destination

https://www.ricksteves.com/watch-read-listen/video/tv-show/milan-and-lake-como

Is your return flight from Rome, or ... ? You can get a fast train from Milan to Rome, so if you need to return to Rome it should be possible to do that in one day. I highly recommend staying the night before your flight in the city of departure so you don't have the possible stress of a transportation delay when you need to get to the airport at a certain time.

take the train; (there will be some connections involved for each);
you can take the train from Florence to Monterosso to explore Cinque Terre.
then take train from Monterosso to Como;
then you can take the train from Como to Switzerland to see the alps;
you have to do a little research yourself to state more specifically where you want to go see the different Swiss alps as they are not all located in one place.

The general wisdom for winter travel is to focus on mid-size or larger cities with more indoor attractions available. You have a couple of those on the list. What about Venice, Ravenna, Padua, Verona?

Both the Cinque Terre and the mid-lake area of Como will have few tourists and a more limited selection of hotels and restaurants open, though of course you only need one in each location. Trains should run as normal. Tourist boats between the Cinque Terre towns never run in winter. On Como, the tourist-oriented mid-lake shuttle boats don't run but other ferries do, as they're used by locals.

The Swiss Alps can also be quiet if there's too much snow/mud for hiking but not enough for skiing. In the Lauterbrunnen Valley, the lift connecting Stechelberg – Mürren – Schilthorn and the nearby Mürren - Allmendhubel Funicular are closed for maintenance through Dec. 8. The area around Lucern would be a better bet, with a couple of good museums available and their aeriel tram maintenance done in November (but cogwheel rail line not running).