Restrict requests to users who are clients.

If the Request was originally created by a client who switched to a vendor, don't show it.

See caveats of Parse query.

"If you want to retrieve objects where a field contains a ParseObject that matches a different query, you can use whereMatchesQuery. Note that the default limit of 100 and maximum limit of 1000 apply to the inner query as well, so with large data sets you may need to construct queries carefully to get the desired behavior."