As far as turning your pedals backwards, a zip tie between the crank and chain ring works great. As far as removing the chain, not something I would do. I rinse off my bike including chain with a low pressure hose and a soft brush after each ride. About every third ride I lube the chain using...
Perhaps for a rail trail ride or an easy XC jaunt. Going OTB at any moderate speed off a jump, drop off or rocky dh with a 4x2 brick in the center of your spine is going to result in additional serious injuries no matter what back protector you have in the pack.
Most important thing is fit to rider. If the geometry is right on the Focus buy it. My 8000 motor on my 2020 merida has been reliable with over 2500km of trail miles.
I was able to test a few different bikes. I'm 6'2 with a short torso/arms and long legs. Levo and Merida both were suitable but Trek was not because it appeared to cater to a longer torso and arms so would suggest a Trek.
I hear they are going to use this for steering as well; replacing traditional handlebars. Joy stick will control forward, braking, left and right. Red button turbo mode. Any truth to that rumor?
The manuals that come with the bike are useless. However the various Shimano manuals you can download from Shimano (basically what Mikerb provided) are quite good and provide torque, detail assembly and troubleshooting details. Most Merida bike PN's can be found on the Merida catalogue archives...
I just use a hose and a stiff brush while backpedaling the Chain. I use Rock and Roll cleaner/lube. Mud doesn't seem to stick but you do need to lube every third ride in really muddy and wet conditions.