Is it necessary to spend minimum 3 hours in office or it will be ok to spend less than 3 hours if your project manager allowed to do so.

Not necessary, you can punch in and out

Hr is closely tracking, many of my colleagues received warning emails. Better to stay atleast 5hrs.

All depends on project to project and management to management..

Latest what i heard from my C5. Less than 3 hours folks are been tracked..