It's six and a half years or so since I visited Russia, to travel on the Trans Siberian Railway and spend some time in a few of the major cities along the railway line, plus some time in Moscow and St Petersburg. But it seems that not much has really changed in terms of dealing with the bureaucracies and their requirements.
I rechecked my travel notes about the visa application process and obtaining the travel invitation. All you need is a series of hotels, not necessarily covering every night - for example, the train nights don't get listed and no one worries about that. Also, plans can change, and that seems to not be a problem. Don't arrive before the visa becomes valid, and it's wise to have a bit of flexibility with the visa being valid for a couple of days after your intended departure date. I got my invitation to visit from a travel agency in London, all done by email, with the invite coming a millisecond after I paid the fee.
It's a very interesting country to visit, and you probably will be surprised (mostly positively) with events along the way. I experienced no problems in Russia, other than finding the limited use of English, but you can be surprised by how fluent some young people will be in English. I think it is best also to be generally accepting of things as they are in Russia, rather than how you might ideally want them to be.