“When the institution you worship issued indulgences, were they valid?”
I’ve never worshiped an institution. You should seriously think about why you falsely claim I do and meditate upon Proverbs 14:5 as you do so. I think you know better than to do what you did.
“Did they cancel sins or shorten Purgatory times?”
No indulgence ever issued by the Church “cancelled” any sin nor did any indulgence ever issued by the Church even claim to do so. Seriously, you’ve never even read a single book about indulgences have you? Have you ever read even one scholarly article about them? Probably not. Have you ever read anything about them that was even reputable? Probably not.
http://www.catholic.com/tracts/myths-about-indulgences
“When the institution you worship IN issued indulgences, were they valid?” Now, how about answering the question. Were the Indulgences your religious institution issued valid?