How does Crowd Control stack with each other?
so stun > snare > slow
Actually this is not correct. They can all be active on a champion at the same time.
Will it keep the 3.5 sec? Or just reset the timer to apply the 1.5 s?
Both stuns will last their normal duration irrelevant of each other. That means that Ashe R will last 3.5 and at the same time the target will have the 1.5 sec stun on him (which of course will expire before Ashe R stun ends).
Slows are a little different though. Greatest magnitude slow is fully applied. While the rest are only partially applied. Their durations are again irrelevant of other slows that are active. For more details on slow stacking you can check the following link.
You can have multiple stuns, slows, snares, etc all affecting you at the same time. They all apply their full effect for their full duration.
That's it, it's that simple.
So a stun does not replace a snare - you are both stunned and snared but since stun stops you doing anything including moving the snare is useless in this case.
For example lets say you are hit by a 1 second stun. 0.5 seconds later you are hit by a 2 second snare. 1 second after that you are hit by a 3 second slow.
In that case you are:
- Stun hits: Stunned only for 0.5 seconds
- Snare hits: Snared and stunned for 0.5 seconds
- Stun ends: Snared for 0.5 seconds
- Slow starts: Snared and slowed for 1.5 seconds
- Snare ends: Still slowed for 1.5 seconds
Even if it is multiple CC of the same type this happens the same way. If you get stunned for 2 seconds then after 1 second hit with another stun for 2 seconds, then you get 3 seconds stunned. This is what people mean when they talk about chaining CC. You hit the target with a new CC by the time the first CC has ended.
When combining slows you do not get the full strength of multiple slows at once. Additionally fears, charms and taunts all force you to move in a specific direction so again they may combine in strange ways. However the general rule here should be clear.
CC does not queue. In the case you described, both effects continue and the character is stunned until both are complete e.g. if a 1s stun is applied 1s into the 3.5s stun, the overall stun will be 3.5s as the original stun will continue through.
Same applies to other effects as they are different modifiers, this applies in the same manner, the slows do not stack but the strongest slow is the one that takes effect.