My mother is 66yrs.old she has broken her chest bone, sternum, two days ago, will she be able to walk up 10 stairs to her apptment, without pain?

Not without pain: Many muscles used in using a hand railing to acend stairs r attached 2 the sternum so initially it will b quite painful and then gradually get better as she heals. If this is in her home u can consider setting up sleeping on the ground floor provided there's a bathroom on the first level. If an apartment the only thing u can consider is a short stay @ a nursing home or with a family member.