It's not important at all stupid.
An IQ test is not a memory test. If you were to memorize the questions and answers then you would still not have an accurate IQ score. Who is this George Costanza.
Alzheimer's - probably below 60
Alzheimers has many levels of severity. It also has moments of confusion interlaced with moments of clarity. It's too flexible to give any proper answer, except to say that it would affect IQ a lot sometimes, and not much at others.
Most IQ tests give short questions based on pattern recognition, numeracy, spatial and verbal. In these types of tests, memory isn't tested so much as cognitive functions. You could, in theory do very well on an IQ test with very little memory use.
Outside of a test setting however, memory will assist very much in problem solving, as real world solutions depend on past experiences as much or more than cognition.
Some argue that memory and cognition have a correlation, other do not. The truth is probably somewhere in between.
Your computer can process problems without its hard drive, but it won't be of much use when the answers are forgotten.
Cognitive functions are based on memory. While you can be cognitive with little memory, you cannot function because you don't remember the necessary response.