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.
Apple dropped 32-bit app support with iOS 11. That means: ipad 4 jailbreak 10.3.4
This is where it gets finicky.
Jailbreaking an iPad 4th Generation Go to product viewer dialog for this item. If you have already updated to 10