Return mode during VIO

howard

Hi,
I am currently using voxl cam with a pixhawk cube and trying gps denied indoor navigation.I had some doubts,

Can the drone return to its home position upon switching to return mode using just VIO?because when I press return switch it just doesn't switch at all , QGC doesn't even give any warning!?
Can I fly it in mission mode indoors?
3.When I was trying figure eight mode in offboard mode , the drone started to go weird and it crashed, what could be the possible reason?
4.Is there any command to know if gps is being used or VIO is being used?
Thank you