If you have already updated to 10.3.4, you are stuck there. You cannot downgrade to 6.1.3 or 8.4.1 without blobs (which you likely don't have). So, your choice is simple: Stay stock and stable, or jailbreak for customization with occasional crashes.
However, if you want to tinker, save SHSH blobs, or use the iPad as a dedicated retro emulation machine, Conclusion: The Verdict on iPad 4 10.3.4 Jailbreak Is there a jailbreak for iPad 4 on 10.3.4? Yes, Kok3shi is the current champion. ipad 4 jailbreak 10.3.4
If you are searching for the term you are likely frustrated by lagging apps, seeking customization, or wanting to breathe new life into an old tablet. The good news? You can jailbreak it. The bad news? It comes with significant caveats. If you have already updated to 10