Comptability support
Trying to provide some answers:


Depends on what you mean by support for accounting, can you define that in a little more detail? CiviCRM can store contributions, event fees and membership fees and will store them with a specific financial type, linked to a financial account. For each of those contributions, event fees and member dues it will also generate financial transactions. You can assign those transactions to an accounting batch, which you will be able to download in CSV format (or IIF out of the top of my head) which you can then import in your financial system.
It is certainly possible to communicate with CiviCRM from any type
of website using the API. So it will also be possible to create
online donations etc. If you want to use some of the standard
generated pages, you can probably do some by including the page in
your Wix website. But it will require some consideration about what
you want exactly, what the alternatives are and what the pros and
cons of each alternative are. Some of the NGO's I work with want
their public website and CiviCRM on separate servers for
security/privacy considerations (and it makes sense IMO). But the
consequence is that some of the nice and easy-to-use form modules
that allow easy access to CiviCRM data need some adaptation.
There is certainly technical assistance from a CiviCRM partner in
your region. There is as far as I know no Core Team technical
assistance because that does not fit into our community model. It
would mean having a big Core Team, while we have a small one
focusing on the core product and a large group of partners focusing
on supporting partners. So check where your nearest partner is
here. All of the contributors and partners you will find on
this list are active in the community and know their stuff when it
comes to CiviCRM. You can obviously also try to find another
organization that is not on the list that says they know about
CiviCRM, but you run a little more risk then with the listed
contributors and partners.