1. Is it open in night time unlike CABA?
Currently There is a lockdown from 23:30 to 5:30. Also, if your DNI ends in 1,2,3,4,5 you can make reservations for restaurants etc. for Monday, Wednesdays, and Friday plus Sunday until 14:00. DNI ending in 6,7,8,9,0 for Tuesday, Thursday, and Saturday plus Sunday after 14:00. Same DNI restrictions apply to stores, malls, supermarkets...
2. is centre of city a good place to stay?
I would prefer something like Chacras de Coria. Small-town charm with lots of restaurants. But still close to downtown, mall etc.
Tupungato and Potrerillos that Bajo_zero mentions are nice but probably very boring now with with the restrictions and colder weather. Maybe more something for a day trip. Same with Tunuyán.
3. Are wineyards open?
Some seem to be open with prior reservation via WhatsApp (same restrictions with DNI number like restaurants and stores). If you are interested in any particular wineyard look for them in Facebook for the latest info on if and when they are open. Weekends are probably better.
4, Is it a fun/safe city to walk around?
Downtown is pretty safe. Other parts are safe, too. But of course there are also less secure parts like Las Heras.
5. how to move around if one does not know driving.
Taxi, remis, Uber, Cabify, bike, walk.
Buses are reserved for essential workers.
6. Things to do apart from wineyards.
Go to some restaurants. Shopping. Bike rides. Parque San Martín. Maybe some day trips to Tupungato, Tunuyán, Potrerillos.
Casinos are closed.