Some questions to making updater

Well now I'm trying to make my own app updater. But I still thinking the method for updater to see the updater version of the app.
What is the best method, file version checking, CRC checking or Hash checking? And how the best way to do it?

One more question. Imagine that I have an application. Then I rebuild it again without modifying any code or event. Is it will have different CRC/Hash?

I'm using MMF2 Developer to let you know.

For first question: hash, especially sha2 is better. For 2nd question - I don't know.

Another opinion?
I used to try File Version checking but there was a bug that the newest version checks the old version as a new update. Now I would looking on Hash Checking or CRC Checking.