Showing child pages and Sibling pages

I have a wp site with this type of structure.

Home page
-Bags
–Red bags
–Blue bags
–Green bags
—Green small bag
—Green big Bag
–Yellow bags
-Shoes
-Hat

I want 2 codes.
First Code:
I want to show links only to bags , Shoes and Hat while visitor is on Home page.
When visitor is on Bags page there should be links only to Red bags,Blue bags and Green bags.

That means i only want to show child pages of current page only no grand child or great grand child.

Second code:
I want second php code to show links to sibling pages only.
Eg: When visitor will be on Home page it will show nothing (there is no sibling to home page)
When visitor will be on Bags page then code will show links Bags,Shoes,HAT.

That means a code which can list sibling pages of current page only.

I was able to find a code some time ago , but my host want down and i lost ever thing. so, i am re-building site from scratch.

Thanks.