What is the highest theoretical chance of freezing a target?

Question

Factoring in the right moves, abilities, items, etc.

Answer 1

If a Serene Grace Pokemon uses Secret Power on Hail/Ice, it will have a chance of 60% of Freezing the target. (30% if the user doesn't have Serene Grace).

Bulbapedia says Secret Power is unaffected by Serene Grace in Gen V, and it is affected in Gen VI, but they don't know if it is affected in Gen IV, VII as well.

If a Serene Grace Pokemon uses a move with 10% chance of freezing, the chance will be doubled to 20%.

Answer 2

Every Ice move that can freeze has a 10% chance boosting to 20% with serene grace