I bought .243 brno for deer, is it good for longshot as if 200 yard +? And I also have a 30 06 winchester?

Truth to tell, I'm not a fan of the 243 as a deer cartridge, having retired my 6mm from the purpose about twenty years ago. But if you're going to use it, be picky with your shots. It'll easily do well almost all the time at 200 yards and more, but you'll have a few more failures than with larger calibers, and the sectional density of the typical 100 grain bullet is still only .242, so steeply angled shots should be avoided. With those provisos in mind, it'll do at 250 and even 300 yards more than nine times out of ten.