Sorry it's not possible. Down at the windows API level, which underpins the .NET framework, a window cannot be created with both a help button and the min/max buttons.
See
Extended Window Styles [
^] and scroll down to the entry for WS_EX_CONTEXHELP where it says
WS_EX_CONTEXTHELP cannot be used with the WS_MAXIMIZEBOX or WS_MINIMIZEBOX styles.
Alan.