Should I bind programs once or each time during render to my pipeline?

Question

I program an addon/addin for another program. This also allows me render stuff for the other program which uses OpenGL. So the problem I have now is that I don't know what program the caller to my render function has already bound if any. I tried to solve the problem with a pipeline. The code I use is this (remember I program in java but your answers don't have to be, I can look up java-equivalents to C/C++-OpenGL functions myself).

int currProgram = GL11.glGetInteger(GL20.GL_CURRENT_PROGRAM); // Get old program
if (currProgram != 0) { // If there was any
    GL41.glUseProgramStages(pipeline, GL41.GL_ALL_SHADER_BITS,
            currProgram); // Bind it to my pipeline
    GL41.glUseProgramStages(pipeline, GL41.GL_VERTEX_SHADER_BIT,
            geometryProgram); // Bind my vertexShader to the pipeline
    GL20.glUseProgram(0);
    GL41.glBindProgramPipeline(pipeline); // Bind the pipeline
} else { // If there wasn't
    GL20.glUseProgram(geometryProgram); // Use my program
}
//RENDERCODE
GL41.glBindProgramPipeline(0); // Unbind pipeline
GL20.glUseProgram(currProgram); // rebind old program

I got two question which bother me right now. First of all like I implicitly said I don't know if the prebound program changes from one call to another. This leads me to the question:

How do I unbind stages in the pipeline? do I just call

GL41.glUseProgramStages(pipeline, GL41.GL_ALL_SHADER_BITS,
            0);

?

Secondly it seems more or less unefficient to bind my own vertex shader everytime I render. I introduced this because I thought there could be more than one vertexShaders bound at a time. If this is not the case I could use GL41.GL_ALL_SHADER_BITS^GL41.GL_VERTEX_SHADER_BIT to bind and unbind the other shaders and keep my shader bound to the pipeline. So question number two:

Can there be more than one vertexShaders bound to a pipeline at once? And how do I rework my code to be efficient?

Answer 1

No just bind the one you need for the specific object. Then bind another for the next object. To "unbind" just bind zero like you did.