Is it possible for a planetary system to form and support life similar to earth-life inside a region of 'timespace' (which is the space within a black-hole), assuming that there is enough space/time for a habitable orbit and for life to evolve into complex forms.
According to the fundamental gravitational collapse models , an event horizon forms before the singularity of black hole. If all the stars in the Milky Way would gradually aggregate towards the galactic center while keeping their proportionate distances from each other, they will all fall within their joint Schwarzschild radius long before they are forced to collide.
... In realistic stellar black holes, spaghettification occurs early: tidal forces tear materials apart well before the event horizon. However, in supermassive black holes, which are found in centers of galaxies, spaghettification occurs inside the event horizon. A human astronaut would survive the fall through an event horizon only in a black hole with a mass of approximately 10,000 solar masses or greater.
So, yes, it is possible to have solar systems inside the event horizon of super-hyper massive blackholes. In respect with the evolution of life... it's hard to tell, for a galaxy-wide black hole to form, the density of stars should be quite high. Which means the radiation from unruly neighboring stars is way higher and the impact of a supernova is felt (due to the smaller distance) much stronger.
One interesting question would be if it is possible to have black holes inside (suppa-duppa massive) black holes.