Here’s my best effort answers to your questions. (@April did a good job of answering 1-4, so here are the rest)
Q5 Do these kind of thermostats control heat and air conditioning, or would I need a separate control for the AC as well as the heating?
They do heating and cooling.
Q6 Are there other thermostats I should consider, such as the Lyric?
A few users use Ecobee and like them. I use a Nest (which I like), but has very poor integration with Smartthings even though official support was promised long ago.
Q7 Will these sensors report the status of the door to the hub, obviating the need for an open/close sensor?
They indicate locked/unlocked. If you want to know if the door is ajar, you’ll need a door/window sensor.
Q8 Is there a cheaper alternative for the garage access door?
Q9 Is there a cheaper alternative for the basement suite door?
Check amazon for cheaper z-wave deadbolt locks. Monoprice.com also sells a generic z-wave deadbolt lock that works.
SmartSense Multi Sensor x 2Detects if the garage doors are open or closedQ10 Will a Open/Closed Sensor work just as well?
Yes, if they are aligned properly. It depends on your garage door and sometimes its hard to stick both sides of the sensors so that they can be next to each other
Q11 Would the Multi Sensor allow me to confirm the temperature in the garage for use in a scene?
It will report temperature that you can use with smartapps
Evolve Z-Wave LFM-20 Fixture Module x 2Actuate the garage doors to open or close themQ12 Will adding this extend the mesh to the garage, approximately 5 meters from the house?
Generally, any plug-in powered (not battery powered) z-wave device acts as a repeater. The range varies depending on what’s in the way. Sometimes you can go 10 meters, sometimes only 1-2.
Q13 Any other danger and damage sensors I should consider?
I use the combo smoke/CO2 detector and moister detectors. You can also put sensors on things like safes and cabinets to tell if they are opened
Q14 What interesting uses have these been put to?
You can have it turn on a dehumidifier (by activating a z-wave outlet) if it becomes too humid, or conversely with a humidifier.
Q15 I’m assuming most people are using these to tell if something has been moved or actuated, but has anyone come up with any creative uses?
You can use them as a switch to turn on/off lights or activate various things around the house.
Wireless CamerasI will have IP Cameras at the front door, back door, garage, and server. These are connected to my home server, which runs software to capture video.
SmartSense Motion Sensor x 0Q16 We’re going to get a cat - how can we stop the beast turning on all the lights? By knowing that we’re all away? Does this mean that if I am home, the cat can turn on all the lights by running around?
Most motion detectors have a limited range (or adjustable range) of view to avoid seeing animals on the ground. Now, if your cat jumps up on furniture, the cat may trigger some motion/lights. This takes some adjustment. Best tip: Put the detectors high enough so they only trigger for humans.
SmartSense CR-2 Battery LifeQ17 How long is the battery life for most of the SmartSense products?
I don’t have these, but most z-wave products last 6months - year on battery. Use amazon to buy a bunch of cheap batteries as replacements.
IFTTTI love using IFTTT and I’m very much looking forward to expanding my recipesQ18 Would it be possible to write a text-based log of events to OneNote, EverNote, or another destination using IFTTT? Has anyone done this?
IFTTT can log certain events (presence, locks, motion, open/close, temperature, humidity, brightness), but not everything. It’s limited. SmartThings keeps a (time) limited log of all events, and I know some people have third-party smart apps that will log as well.