I94 shortened at poe

At my poe i have shown my visa and my latest approved extension copy which has a start date 2 months from now , but cbp officer did not give me admission based on that instead provided until current h1b petition end date . I checked with attorney and he auggested me to cross border at mexico and get i94 extended . Can that be done at laredo border ?

Yes, this is doable.

It did not work . They have not extended my i94 at Laredo border . Now my employer is willing to file H1 extension for me . My wife has not travelled with me and was in US while in entered US .

Now my question would be , if her extension has to be filed as well if my employer files my extension

Yes, ideally you should apply for H4 extension of status with you H1b.