Can a replacement of partner in a partnership with 2 partners be made to retail pan card

Dear Sir,

We applied and have a PAN card in the name of a Partnership firm and had 2 partners. Now one partner has taken a retirement from the firm and moved on. What I would like to know is -

1. Since the only one partner (myself) left in the firm, the constitution of the firm would change to proprietary. So, what happens to my PAN card taken in name of partnership firm?
2. We had registered our firm under GST and have a GST number with the PAN card of partnership firm. So, in that case, I guess, my GST registration would also change. Am I right?
3. If I add another partner in place of the retired one, if I can, can my PAN and GST registration be retained and I continue with transactions with same registrations? Or both, PAN and GST will still need to be replaced?

Regards,

Jayant.