As has been stated before, the stone ritual is supposed to represent baggage you are leaving behind. But honnestly it is a pain for the local authorities to clean up with tractors of all sorts, and costly. Because these do need to be removed and are removed.
Some people have expanded the stone idea and bring teddy bears, photos, trinkets, and all these end up making a mess, flying away, etc. Is there really a symbolic gesture meant to represent a fesh start and old baggage that needs to polute someone else's environment and surroundings? I think we sweat quite enough to get "the uglies out" without poluting and causing our hosts to have to endure cost and time to manage our symbolic gestures. And you will see items left everywhere, many on frost fences.
So not only is it not a requirement but rather a pain for those who have to pick it up. I would encourage you to think if this is really something that will make a difference in your life so that you feel you must do this. Bring a piece of inscent to burn if you must, at least it won't linger there for others to deal with.
As for companionship you will find many people along the Frances to keep you company if you ask them to walk with you. But these days it is becoming rare not to see people in the front and back so you should feel safe. Leave after the sun is up, stay on the Camino, walk at a rate that is comfortable for you so you don't injure yourself and you'll be fine.
I know how this undertaking can seem like something uber exotic, but the second you start walking those fears and anxieties will disappear. The truth is that on the Frances you are walking from village to village, you are not on a remote excursion of any kind. But don't be afraid to ask for companionship, surely anyone you meet at an albergue or a cafe, or passes you on route can walk with you for an hour, and then someone else picks up the baton.
I know I have asked for company at the end of a long day when it seems I will never make it to my destination and need the distraction and motivation to put yet again one foot in front of the other.
You will have a wonderful time, just put one foot in front of the other.