Hi,
For the gateway patch you need to check the below note.
This note states which all patches are needed for NW 7.4.
1942072 - SAP NetWeaver Gateway 2.0 Support Package Stack Definition
How should you install the gateway component in NW 7.4.(Should use MPOZ to generate the XML file ,so install the NW 7.4 first and configure this system to Solman and use MOPZ to get the stack file to install gateway component)
1931992 - Error: Conflicts between Add-On GW_CORE 200 and other components
This note says that NW gateway installation is supported as addon in NW 7.4 but read the below lines.
The following Add-Ons are only technically and not functionally
released. I.e. installation/upgrade is supported, but productive usage is not supported:
1826531 - Add-on compatibility of SAP NetWeaver 7.4 - ABAP
Try to used the below note to install the gateway.
1569624 - Installation/Delta Upgrade of SAP NW Gateway 2.0
For the installation of NW 7.4 please check the installation guide.
Thanks
Rishi Abrol