Shell Programming and Scripting

I have a file say g1.txt and content of this file is as below
1|HideCDrive, | : REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v NoDrives /t REG_DWORD /d 4 /f ,
2|HideRunButton, | : REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v NoClose /t REG_DWORD /d 1 /f ,
3|DisableControlPanel, | : REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System" /v NoDispCPL /t REG_DWORD /d 1 /f ,
4|AddMycomputerIexploreandMynetworkplaceMyDocumentIcononDesktop, | : REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Explore\HideDesktopIcons\NewStartPanel" /v {20D04FE0-3AEA-1069-A2D8-08002B30309D} /t REG_DWORD /d 0 /f ,
5|RestrictUserToRuncmd, | : REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v DisallowRun /t REG_DWORD /d 1 /f ,

Content of g2.txt file

REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v NoClose /t REG_DWORD /d 1 /f ,
REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System" /v NoDispCPL /t REG_DWORD /d 1 /f ,
REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Explore\HideDesktopIcons\NewStartPanel" /v {20D04FE0-3AEA-1069-A2D8-08002B30309D} /t REG_DWORD /d 0 /f ,
REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v DisallowRun /t REG_DWORD /d 1 /f ,
REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Uninstall" /v NoAddRemovePrograms /t REG_DWORD /d1 /f ,

I want to create a script in which user enter numbers say 1,2,3 when user enters 1 it will get REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v NoDrives /t REG_DWORD /d 4 /f , from g1.txt file and so on......and it will check REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v NoDrives /t REG_DWORD /d 4 /f , already there in g2.txt file or not if exists delete that line. using grep commnad

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--ahamed