Hello,
For the first question, you can undo the ignore setting. For this, select the parent folder of that file and after that look in the Properties view. There should be a svn:ignore property having as value the name of your file or an expression that matches the name of your file. You should select that property and remove it by pressing the red X button in the view's toolbar. After this, you should be able to see the file in your working copy marked with a '?' icon, meaning that it is unversioned. To make him versioned, use the Add... option from the file's contextual menu. Now you would be able to commit it on the repository, but pay attention that now there is no solution for your problem.
For the second question, there is nothing that can be done about it. SVN does not offer such type of support. Neither Syncro SVN Client, but I've added an issue on our internal issues tracker to add filtering support in our application. The only thing you can do is when committing to be very careful not to commit that file (to not send modifications to the repository), and when updating to be very careful not to update that file (to not override your work with the modifications incoming from repository).
On the moment when we will have a solution implemented for your problem we will notify you about his availability.
Best regards,
Florin Avram
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Syncro SVN Client
http://www.syncrosvnclient.com