Hope you all doing well.
Can I please get a suggestion on how to cover cracks on walls and ceilings
If the cracks have been there for some time and haven't just appeared recently, then you can use Polyfilla 100g Plaster Cracks Filler on them. You then must sand the excess filler back and undercoat before painting.
If the cracks have only just appeared, you might like to secure the cornice in place first with plasterboard nails before filling. This will help stop the cracks from getting larger and requiring another application of filler.
You should find this step-by-step guide useful: How To Repair Cracks In Plaster.
Please let me know if you need further help or had questions.
Thank you so much, @MitchellMc. Very informative. Crack all filled and ready for painting this weekend .
It would be great if you good update us with some pictures once you have finished the job. I trust it will look fantastic.