Questions 1 and 4 are duplicate:

Answer of Q1: Inserting RecyclerView items at zero position - always stay scrolled to top

Answer of Q4: How to fix RecyclerView shuffling issue:

overriding these two methods in Adapter will solve the shuffle issue.

@Override
public long getItemId(int position) {
return position; // or item id
}

@Override
public int getItemViewType(int position) {
return position; // or item id
}