Hi, it is difficult to make out many specific details from either your photos or those you link to. I'd suggest that the figure with the puttees/bolt action rifle is quite possibly 1897ish British. I don't think he's German as the Seebattalion figure has a crest on the front of his helmet. The figure in the gaiters and armed with the Martini-Henry is Zulu War era.
Your question re: cavalry - again the photos aren't the best but there are lots of minor uniform differences, the weapons are different and the earlier one wears boots, the latter has shoes and puttees.
For photos of troops in India in the 1890s I'd suggest "The Frontier Ablaze" if you can get a copy at a reasonable price, or the relevant Osprey "British Army on Campaign (4)" (though that covers not just India).
But again, as discussed in the Afghan War artillery thread it is largely up to you what you want to do, especially for VSF. If you aren't really fussy about detail then just go for it, mix and match. If you are fussy then it sounds like you've got 2 batches mixed up with uniforms and equipment 20 years apart.