#1 - 0 PIPs if it is march move.
How much does it cost for a group with two ranks of pike for it's first march move if it includes mounted?
0 or 2 PIPs because it depends.
Page 28 : "No PIP is expended by a first march move this bound if ... a group headed by 2 or more complete ranks of Pikes that is moving straight ahead." The PIP penalties only apply to moves requiring PIPS : "I extra PIP is expended by a move requiring PIPs...etc.".
So if the group is headed by (and only headed by) at least 2 complete ranks of Pike then the move costs 0 PIPs, even if the group includes mounted elements (say in the third rank or on the rear of the group). But it must be a march move and it must be straight ahead. If this is going to get debated it I suspect it will be around the meaning/interpretation of "headed". Take for instance a group comprising a pike block with mounted trailing 'wings' aligned on the 3rd or 4th rank. I personally don't see an issue with such a formation expending 0 PIPs for its first march move straight ahead....not that I would naturally choose such a group but it's possible.......because I view the pike elements as being the 'head' of the group given other non-Pike elements are aligned on the 3rd or 4th rank.
If the mounted elements are in either of the front 2 ranks (of the 'head') then the move will cost 2 PIPs because the group doesn't meet the criteria for the 0 PIP move, and you have moved foot and mounted elements together.
I'm not sure what you are driving at with your third question but given the constraints of march moves, and provided you meet the criteria outlined above, the first march move in a series of march moves still costs 0 PIPs - unless I'm misunderstanding something?
Andrew