[Mp4-tech] [H.264] Is slices based on only a picture or on whole picture sequences?

[lurui]

Dear expert:
    I know slice is part of a picture, it means a slice can be reconstructed independently of other slices within a picture level.
    The question is:
    1.If a slice of a picture lost, can the deblocking procedure correctly do without the lost slice?
    2.Can motion search across the slice boundary of the slice of the reference picture? For example, if the previous reference picture is composed by two slices--the upper slice and the bottom slice,can a MB belongs to the bottom slice of the current picture search it motion vector that points to the upper slice of it previous reference picture or even points cross the boundary of the slices?
    3.Does the slice number and size and start-end postion must be same for every picture under a picture sequences to encoded?
lurui