Tallis For Kaddish D'Rabbonon, and at a shiur

I understand that it is fitting and proper that the person reciting Kaddish Yosom [Ovel or Yahrtzeit], wear a tallis and stand next to the Chazzan while reciting Kaddish. Does the same apply to Kaddish D'Rabbonon? At a seudoh mitzvoh, like a siyum for a masechto is a tallis required for the one making the siyum?

Shalom.

Rallis

I give a גמרא שיעור before שבת מנחה which in our shul occurs directly after קידוש following מוסף.

My questions are:

1) Should I wear a טלית since my שיעור is in the Shul itself, though NOT directly in front of the ארון קודש?

2) After the שיעור the Rov instructed me to recite "רבי חנניא" so someone can recite קדיש דרבנן. Sometimes that person is myself. Should I therefore, wear my טלית so that I don't have to be מטריח the ציבור to grab my hat, jacket and טלית and move forward to be beside the Omud to recite קדיש דרבנן?

3) If I do wear a טלית do I take it off for the beginning of שבת מנחה since I am the גבאי and as such wear a טלית for קריאת התורה?

Rallis

On Friday night, does a mourner take off the tallis after saying kaddish? I vaguely recall R' Hamburger saying that person with a yarzheit should keep the tallis on for the entire minyan but a mourner should take it off after kaddish. My recollection of that conversation is hazy though.