... Is it safe to downgrade? Are there security risks? ...
As a general observation, the further back one reverts to an older software version from the latest one, the greater the chances (and numbers) of possible security risks to which one might become exposed. This is especially true for versions within a given family of software which undergo frequent updates that include security patches for the software code. On the other hand, reverting to an older version possessing an entirely different underlying code framework may not present as great a security risk as otherwise reverting within a family whose versions all have the same framework, provided that the old software's framework had the vast majority of its security bugs fully wrung out of it and provided new classes of exploits haven't arisen since then that implement attacks upon elements of that old architecture.
The main problem with using any old and now-unsupported version is that it won't be security-patched at that version level should a new vulnerability arise. Most users of old versions might not even realize such a vulnerability affecting them had appeared 'in the wild' unless they habitually stay current with new exploit news and CERT vulnerability reports.
