I usually complete a from-scratch model within a week. While working on a project, I will reply to messages within a 24 hour cycle. I will post WIP images as I progress.
No. You must upload the model to VRChat yourself. I will provide you with a unitypackage ready for upload.
I will not walk you through the steps of how to upload the avatar. There are plenty of tutorials that will show you how.
If you find any issues with the avatar itself in the process, please do let me know.
From Scratch models do not use a basemesh, but rather are modeled from the ground up.
Visemes are mouth shapes. The primary method of avatar lipsync in games like VRChat is for the avatar creator (me) to create 14 blendshapes, also known as shapekeys, for each phonetic Viseme. Each visemes can be created manually. The cheaper alternative is to create the 3 most generic visemes manually, and then automatically generate the rest from those 3.
In order to animate properly, a 3d character needs a collection of bones known as an Armature. The bones must be weighted to the mesh, usually by a process called weight painting. This collective process is called rigging and is a necessary step when creating avatars. Otherwise, it will remain T-posed indefinitely.