I have an IPB3 forum which uses 3.4.7 from late 2014 which I have just restored from a backup. I cannot upgrade to IPS4 right now due to the size of the database. This will take a few weeks to figure out. The only option seems to be to put up the 3.4.7 backup of the forums until then. I have asked the IPB team for the latest version of IPB3 to fully secure the site until I can upgrade to IPS4 however they denied my request. Can you see there being any problems using 3.4.7?