Joint Tenancy – Details I was on title as joint tenants with my parents, but…

Joint Tenancy – Details
I was on title as joint tenants with my parents, but now I’m on title as joint tenants w/just my mom (who is about 80). She has said o.k. to gifting over the other half of the joint tenancy to me. if she goes ahead and does this…

Question:
#1. Can the gifting or deeding over of the other part of the property be contested?

#2. I do not have nor want to have ”financial power of atttorney” for my mom other assests (savings, etc.), but if someone else has or gets power of attorney (be it a friend or family member), can they quit claim or somehow transfer over her half of the joint tenancy property to themselves, or to a trust for my mom?

quit claim deed & probate 3 years ago mother passed leaving house to sister(we…

quit claim deed & probate
3 years ago mother passed leaving house to sister(we thought!quit claim deed)now we find out house has to go through probate with all siblings involved!have been maintaning house to keep mentaly handicaped brother in “his” home.circumstances changed brother is in group home now.house up for sale,have buyer but we find sister is not owner of house.Problem; house cannot go for sale untill all siblings contacted!Do not know where 2 brothers are –can the mortgage NOT be paid thereby turning house back over to bank?and walking away from this mess!hernando county fla