Can you use jaggery as the sweetener? If yes, should the quantity be the same as that given for sugar? Should gur be melted down in water, and will water affect the pickle? Should gur be added at approximately the same point?

Yes, jaggery can be used in place of sugar. I is dark brown or Muscovado sugar quite often.

You grate the gur, no need to mix with water/boil. And yes, you add it at the same stage as sugar. Gur is a type of sugar after all.

Hope your pickle comes out well.

Mine was too sour, so I added figs. Weird, I know, but interesting.

Well why not Phil! This is how new recipes come about.