Does consuming calcium tabs or lemon will be a precaution from corona virus?

Vitamin C helps build immunity and fight off infection. There are umpteen foods rich in Vit C like gooseberry, oranges, lemons, etc which you can have. However, Vitamin C cannot cure or prevent COVID 19 in particular. Do not take supplements unless prescribed by your doctor.
There is also no evidence that calcium helps in preventing COVID-19 infection. However ,there have been some studies that show that irrespective of the illness, the mortality rate of patients with low calcium levels was significantly higher than the mortality rate of those with normal calcium levels. If you are low in calcium , you could correct that with diet or supplements [ to be taken on medical advice only ].