The engine in MK1/Facelift is defo the same engine the cam cover is different as it has Zetec S written on in your first link the same engine later featured a diffrent cam cover in your 2nd link with "Zetec SE" printed on it.

The same engine is also in the MK2 Focus but now comes under the Duratec name. This head maybe different as the model is avaliable in two power guises 100HP which the MK1 had and 115BHP (TI-VCT) the extra power is in the VVT.

TI-VCT - Twin Independant Variable Cam Timing

On the "Zetec S" cam cover the plugs are covered in and you need to remove the cover first, the cam covers may be interchangable but don't quote me on that.

The Blacktop/Silvertop are the two litre Zetec's which are totally unrelated to the Sigma family.

Edit: To add both of the links you mention are from Focus Mk1's

Martin