Hi Juhi, first of all, these are not button they are the custom link which works as the button and you can't hide these Links with salesforce setting an idea for this hide and show are given to salesforce success community. follow the link https://success.salesforce.com/ideaView?id=08730000000ksRdAAI
but let me know you that you can override these custom link with a visualforce page and make some configuration Let me know if this was helpful
first of all, these are not button they are the custom link which works as the button and you can't hide these Links with salesforce setting an idea for this hide and show are given to salesforce success community. follow the link
https://success.salesforce.com/ideaView?id=08730000000ksRdAAI
but let me know you that you can override these custom link with a visualforce page and make some configuration
Let me know if this was helpful
Thank you
Avaneesh Singh