candling eggs questions?

[nfrost]

Does anyone have a picture of a good and a bad eggs at 4-5 days, I have one that's starting to get a little veins, but all the other 10 u can see the tikl but no veins but darker in the center of the yolk any thoughts?

 

[nfrost]

P.S. How long can a hen sit under a egg before it gets rotten and explodes, can i leave a egg under a hen the whole 21 days to just see if they hatch, or will they explode before that!!