Could I take vitamin D3 as 10000u twice a week if I am not exposed to sun. I had a deficiency one year ago but now it is normal with the supplement.?

Yes. Most adults need at least 2000 iu daily and you will get that much. A toxic level is 20, 000 iu daily or more and you are far below that amount.
Sure. That is a very reasonable dosage. Pretty much everyone north of the 45th parallel needs to supplement their vit d as you don't get enough sunlight to make enough on your own.