We have to take the languages into account. So at least for the testing phase should be the solution in the regional language.
The consortium presents a proposal at the issue of the tender. The consortium should stay the same in the three phases, BUT: If a company goes bankrupt they can leave and the consortium can then replace them with another. But that's only an exception.
But a consortium can subcontract another company if they need development and research in an area they cannot cover. But they can't add a new company to the consortia (so they get money from the project. If they're a subcontractor, they get money from the company in the consortia, not the project)
We suggest to define agreements within your consortia to ensure that IPR and confidentiality is in place.
June 2015 at the earliest, depends on the legal and administrative issues
No, the main interest is to cover all of the requested functionalities, so it's up to the bidders to decide if they want to create consortia or bid alone