Hi Glide! Thanks a lot for your help! I have followed your advice to use file 3dfxvs.dll from SFFT Driver Alpha 39 and video overlay became available! 
. But I do not clearly understand what about D3D features in this case. As I mentioned before, I have learned from this forum that using file 3dfxvs.dll from AmigaMerlin 3.0 also make overlay available, but at the cost of D3D features. I would pay your attention to the fact that I have not tried to use 3dfxvs.dll from AmigaMerlin 3.0, so I can not understand what means such "D3D disappearance" at all... At this moment I can change settings here: 3dfx Tools Hub > 3dfx Advanced Features > (here is some sort of tree structure) 3dfxTools Advanced Features / Direct3D / ... and so on — does this means that my D3D works properly? How can I clarify this?
. But I do not clearly understand what about D3D features in this case. As I mentioned before, I have learned from this forum that using file 3dfxvs.dll from AmigaMerlin 3.0 also make overlay available, but at the cost of D3D features. I would pay your attention to the fact that I have not tried to use 3dfxvs.dll from AmigaMerlin 3.0, so I can not understand what means such "D3D disappearance" at all... At this moment I can change settings here: 3dfx Tools Hub > 3dfx Advanced Features > (here is some sort of tree structure) 3dfxTools Advanced Features / Direct3D / ... and so on — does this means that my D3D works properly? How can I clarify this?
. I mean this setting: 3dfx Tools Hub > "3dfx Color" Tab / "Selection" Group / "Video Overlay" Radio Button — this setting is "grayed out". I have searched through this forum for solving my trouble and found one interesting solution: replace file "3dfxvs.dll" from current driver kit (i.e. AmigaSport v.3.0) with file "3dfxvs.dll" originated from another driver kit — AmigaMerlin 3.0. But this solution has significant drawback resulting in losing D3D capabilities (because the new Amigamerlin's D3D section have lost the compatibility with Voodoo_3 card).