Rollback in github

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ASP.NET

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Please help me regarding this issue

Currently i have re-pushed and committed all my changes and local and remote "Master"
is at 0 in fig.

1)i want to revert back all my changes from remote and get it back to at 1 positions in fig. This is same branch "MASTER"

2)i want to revert back all my changes from remote and get it back to at 2 positions in fig. This is Different branch "Umesh_.."

Please see the picture
https://i.imgsafe.org/60b5e00.png[^]

What I have tried:

i have tried these commands " git checkout master@{2009-07-27 13:37}" but not working