There is two question-suggestions:
1-st) can I somehow change wrench's building menu (make it custom or add new pages or implement images)?
if not - do it pls

2-nd) can I somehow make custom buildings using construction zone(building 10) which uses cs2d's pattern?(would be good to have it's source code or at least implement ability to add custom breakable objects to make more constructions).

as far as I know there is no possible ways to make custom breakable with specific command, except using image and imagehitzone, but compare to cs2d's built-in BUILDINGS which might work easily with the way cs2d-editor do it (env_breakable) and ability to use built-in BREAKING/DAMAGING buildings with correct HP show, without making lua for it to get HP output(not to use mousemapx/mapy and in case of worse ping or connection problem u see delay of all actions). Makin WALL III and place image over it for example custom turret(rocket launcher or whatsoever) would not look like (Rocket turret made by Mora) but like (Wall III by Mora). not good tho

the construction mode in this game might be very much nicer and bigger if two upper things might be changeable/implementable.
/thanks

You can create custom menus with menu or just pure images with image.
Check this out: https://youtu.be/kPpc7BQVgtQ


You can but it's a mess of perfect timing.
Check this out: https://youtu.be/lTnDVz8bTV4
The explosions were not present in the final build, as I switched to killobject.


I'm not sure, but it seems that the env_breakable entity is very sensitive and not dynamic enough in the sense that you can just spawn it mid-game.
Which is likely the reason why you can't re-spawn said entity through the editor.
You can disable those HUD texts with mp_hud and make your own hover HUD texts with image, hudtxt and always.