Wooden edge around hearth tiles, correct glue & grout, cutting fibre cement sheet?

We are putting a wood heater insert into an existing old fireplace in our house in Melbourne. It's a heritage listed property (this section of it from the early 1890s) so changes need to be minimized. The existing fireplace is 460 deep and 900 wide, with a brick hearth that comes out another 300 and is just over 1300 wide. The bricks are about a half inch above the level of the surrounding pine floor. The new hearth needs to come out about 580 from the front of the fireplace, not just the 300 of the old brick hearth, as the new insert sticks out 80mm and I must add 500mm of hearth in front of that. The new hearth will need to cover all of the old bricks.

So...I've bought a piece of 18mm compressed fibre cement sheet as a start. My wife is chasing up the tiles for the visible part of the hearth. I will get cheap tiles for the part hidden under and behind the insert, so as to have a flat surface to slide the insert back on to. But I have construction questions.

1. I'm planning to cut the fibre cement sheet with a metal blade in a jigsaw, wearing a mask. Is that OK?
2. What glue is best to use? Something with latex in it? I know I need some degree of flexibility as it will repeatedly heat and cool through its life.
3. Likewise, what grout?
4. I will make a wooden edge for the hearth out of leftover redgum from the restumping. It will be L-shaped in cross section going back under the fibre cement board (to hold the outer edge of the hearth up off the floorboards, with a few more thin pieces of wood where there are joists underneath), coming up the front of the fibre cement and the tiles. How do I fasten it to the fibre cement board best?
5. What product do I use for leveling the bricks that the rear part of the fibre cement will rest on?

thanks in advance....

Andrew

To cut the sheet, use a diamond cutting disk in an angle grinder.

https://www.bunnings.com.au/flexovit...blade_p6370870

A metal jigsaw blade won't last - I've tried it. I was originally going to recommend shears from the green shed but read you are using 18mm and their only good for up to 10mm

I would use some self levelling compound for the bricks in the back, its like really runny concrete without the aggregate. There are many different brands but one I know of is called ardit. As for gluing the cement sheet to the bricks, a tile adhesive would probably be what you'd want, I would recommend going to a real tile shop, not bunnings, and asking for what they recommend for your circumstance. They will help with grout also.