Parameters to create projected SRS. Some of parameters have defaults. Some parameters have reasonable defaults, so you don’t have to assign only them. If you assign null to those parameters, a default value will be used. ProjectionMethodName and Base don’t have defaults - you have to assign some non null value to this properties.
Base geographic SRS (SRS to which projection is applied). You MUST set this property to not null value in order to create valid SRS, this property does not have any default.
Identifier of projection method. There is no default value, you might set this parameter to not null value, if you want attach identifier to projection. If you do so - its up to you to ensure that identifier in consistent projection method name (projection method name will not change when you set this property).
Name of projection method. There is no default and you MUST set this parameter to not null value, since projected SRS with no projection name is useless.