To your 2-nd question - there is a gameplay constant to change how long bones remain on the ground.
To your 3-rd question - in GUI there is an action called "Revive hero instantly". It doesn't work only for heroes tho.
You can revive the unit, give it locust, pause it, and make it play its death animation. Then after some time, make it play its birth animation (if it has any).
As per "can you detect how long is the unit's death animation" - I don't know (probobly not).