Answer:
For the Soviets to win in Afghanistan, you have to get China, the Muslim nations and the US to stop supporting the Mujaheddin. Assuming the Soviets manage to pacify the entirety of Afghanistan, either by destroying the Mujaheddin or by forcing them to go to Pakistan, i don't think that they would have pushed against either Iran or Pakistan. Maybe they can coordinate with the Americans some sort of joint invasion of Iran, but Reagan wasn't much of a fan of the Soviets so i doubt they could have worked anything together, i think the contrary will happen, the occupation of Afghanistan will be even more demonized than in our times. As for Pakistan, they were allies of the US, and Reagan wasn't gonna stay still if the Soviets started conquering Pakistan. Plus Pakistan has their nuclear deterrent, and its religious fanaticism, so the Soviets are going to have an even worse time than in Afghanistan