Mouse : the top row in the pick box.
Keyboard : the equivalent key, for eg for 1 press key 1 and for A press key a, also num pad works (make sure num lock is turned on).
Mouse : the bottom row in the pick box(consider doubt text as pencil in is disabled in settings->settings->preference).
Keyboard : the equivalent key + SHIFT.
Mouse : the bottom row in the pick box(consider doubt text as pencil in is enabled in settings->settings->preference) or numpad(with num lock turned on and keyboard cursor is not present.
Keyboard : the equivalent key + ALT(num lock turned off).
Mouse : middle click
Keyboard : 0 key, if numpad 0 then num lock must be turned on.
There are three modes such as sticky selection, no sticky selection, partial sticky selection(default). In sticky selection both pick box and puzzle box is left selected. In no sticky selection, both pick box and puzzle box are unselected. In partial selection the first clicked will remain selected and last click selected will be unselected. The right click will clear all the selection. You can change these options in settings->settings->preference.
settings->settings->preference->keyboard cursor move over fixed box is self explainatory. settings->settings->preference->keyboard cursor no border restriction is also self explainatory. Use arrow keys to navigate or k=up, m= left, ,=down, .=right to navigate