how to relinquish intestate heirship?

you can relinquish your rights in favour of your mother by simple relinquishment deed or you may gift your shares through gift deeds. 

The relinquishment deed is the step 3 suggested by my lawyer, to remove our (3 brothers) name from the RTC changed in step 2. Can I use the relinquishment deed in Step 1, to have our (3 brothers) names not be in the legal heirs certificate?

just at the tme of getting heirship certificate u can relinquish ur right and get the certificate in mother name only or u can execute relinquushment deed

Unfortunately, there is some confusion with the nomenclature. What I refer to as "legal heir certificate" is the one issued by the Taluk office through the VA/Tahshildhar route. Today I came to know that it is also called the Survivorship certificate. My lawyer says the VA/Tahshildhar will not regard the relinquishment deed.

Is there some way to have only my mother listed in such a certificated?

Sir, If you desire to register relinquishment  deed you can in the Sub registrar Office. All are legal hires, Survivers hence revunue department will issue cerfificate with all names.

Besides you four members can enter into partition deed giving all Immovable property to your mother in one schedule and keeping family cash or movables with others as one share.  This partition will give effect all rights to your mother as desired by you.

I now understand from the replies in this forum (and as already explained by my lawyer earlier), that there is no way to do this in one step. I first need to get survivor certificate, then get RTC changed to our four names, then get relinquishment (or partition) deed, and change the RTC yet again to my mother's name. If I have understood wrongly, or there are simpler alternatives, please let me know. Otherwise, thanks everyone!