I'm sure we can help you fathom what works best in your circumstances

.
You will find there will be some differences of opinion, even here

, about some elements of feeding and weaning. But what that actually tells you is that there is no one "right way", that a variety of techniques have benefits and downsides - so don't be too fearful that doing or nor doing any one thing in a particular way will kill your little charge.
Unfortunately, the fact that we have all evolved our own specific ways of doing things to avoid problems we've had in the past also tells you that sometimes these lambs don't thrive, even when very experienced people do their very best to avoid all the pitfalls they know about.
Yes, a cade lamb will do better with creep, at least until 4-6 months, and may need extra rations through winter. However careful we are, we can't give them as good a start as being reared by a lactating ewe will do, so they'll need more support for longer. Lambs being reared by their mothers get milk until weaning, which a farmer might do at 4 months or so, or might let the ewe do it herself a while later. Bottle lambs get weaned much younger, usually by 8 weeks at the latest, so they need some other way of getting the nutrients that the other lambs are still getting from their mothers' udders. So most guidance about weaning is going to talk about how much creep the lamb needs to be eating before it's safe to wean it.
Yes they need to eat forage - grass, hay, straw - to develop the rumen. Ideally they have access to some forage from within the first week.
Creep isn't necessary for rumen development as such, but ruminants need the gut flora established to digest whatever feedstuffs they're eating, so as we want the weaned lamb to eat some sort of cake for a while after weaning, we start to introduce it at around 3 weeks to get the rumen used to it well before the lamb needs to rely on it.
Personally I like to use a pasture mix rather than a specific (and higher protein) pelleted lamb creep feed. The variety of sizes, shapes, textures and shapes makes it more interesting to the lambs, and I find they'll start to pick at it (and probably eat the peas or the maize flakes only at first) earlier. (It's cheaper and usually lasts better too.)
Before giving you specific advice about your lamb's feed size and number, we'll need a bit more information.
How old is she? What breed of sheep (ewe and tup)?