Maya basic functionality (like selectAll, select child objects) questions from 3dsmax user

sergsse

Hey guys! I am trying to switch from 3dsmax to Maya and got many issues on the start. Could anyone please help:

1. SelectAll is actually selecting top parent objects and highlighting the rest but I want actually to SELECT all (for example to add a key to everything at current frame (this is not the only case)). Is it even possible in Maya?
2. I can select a parent using Up arrow button but it looks like there is no way to select a child object(s) - it would be logical for a Down arrow button to do the job but the only way I found is to use a script ("select -hi") which leaves a parent selected which is not good but is there are a simple option to select child object(s)?

I appreciate "select -hi" can be a solution for [1] but I believe there should be a simple way to select all unfrozen objects