I don't think so.... But its better to maintain some what constant CTR. And also I heard thet CTR which is better is less than 10 is more good.
Nope, Always try to hope to stay under 30% it's a red flag., shoot for 10% and under. However there are no limits, you can go up to 100% for a day; I have done this before when I first started off.
If your CTR is high and clicks from your site are not benefiting the adwords publishers, then there is a strong case against you. Else it is fine.