[negfrequency]

I have no idea about the first one. However, the latter 2 i have run into multiple times. Generally the update will give you the results you want, but if your unsure go for the "no". itll ask you again the next time you open it, (as long as you didnt save it) .

The third error is just a result of changing objects that have constraints applied. Id just delete the constraints it complains about, and if you want them there again just reapply the necessary ones and it wont complain like a child anymore.