OD1P - Aug 9 Problem / Failure

Failure 1  

The white stone captured by 3 only makes a false eye.

Failure 2  

White makes a four-point nakade. Black is dead.

Failure 3  

Black lives in the corner, but sacrifices six stones.

Solution 2?  

mgoetze: Since this is not on the solution page it must be a failure... could someone show me the refutation please? :(

Failure 4  

Gorobei: this looks bad.

mgoetze: Hm, now how did I overlook that white 4? Wouldn't be a problem if it didn't put the stones at the right in Damezumari.

tapir: Hm, am I missing sth or is Black alive after at a? I am missing sth.

Failure 4 - II  

unkx80: How about this?