ios downgrade

Have you tried Restoring your iPad in iTunes?

Downgrading the iOS is not supported. If you have a problem, there is a solution. Try defining the problem rather than ranting.

Here is my updated list of suggested fixes for a slow iPad 2, 3 or 4 (and 1st gen Mini) models.

Try resetting All Settings found in the Settings App under General and in the right column under Reset.
Try resetting histories and deleting/resetting caches in all of the web browsers you use.
If you use Safari, these functions maybe in the Settings App under Safari.
Other web browsers have their settings inside of the running app, itself.
If your iPad has been activated for iCloud, in the Settings App under iCloud, to the right, under iCloud Drive, tap iCloud Drive and make sure Safari is turned off for saving Safari data to iCloud Drive.
Also, under iCloud in the Settings App, in iCloud Drive, disable the saving feature for any other apps that you DO NOT want data being saved automatically to iCloud Drive.
If using Safari is still causing issues,
Try changing/using another, different third party web browser.
I don't use iOS Safari too much any longer because I found it causing me some headaches on certain websites I, regularly, visit.
I commonly use another third party web browser, Perfect Web Browser (there are others that may suit your web browsing style better, so look at all of them first to see which third party browser may work better for you) and I never experience a lot of the issues that Safari was causing.
In the Settings App under the General tab, to the right under Spotlight sesrch, try disabling the search under apps that really do not need a search, like some games, remotes, apps that really do not need to be searched, etc., to reduce the list for Spotlight to search.
Try turning on Reduced Motion.
This is found in the Settings App in the General tab the left panel.
In the right panel look under Accessibility, the look for Reduce Motion and turn this feature "On".
You should see an appreciable performance increase on all iPad 2, 3 and 4 models.
In the Settings App under the General Tab, in the right column, look for Background App Refresh and turn this setting to "off".

If you do not use Find My Phone/iPad, try turning off/disabling this feature, also, to see if this improves your iPad's performance or not!
Try a reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

Good Luck!

Failing all of this,

Here is my own restore procedure that has already worked, sucessfully, for a couple of iPad 2 users, so far!

First, connect your iPad to USB and sync and backup your iPad to iTunes (make sure your iTunes is up to date).

Then disconnect/eject your iPad from the computer.

From just the iPad, in the Settings App under the General setting, look in the right column for Reset option, then erase and reset your iPad to completely erase your iPad and then, again, from the iPad, set it up as a new iPad setup to factory "out of the box" operation.

Then reconnect your iPad to the computer and make sure to cancel the syncing, by tapping the small X to the left in the top center iTunes display box.

iTunes should detect your iPad. If iTunes begins to try and sync, again, cancel the sync.

Select Restore from Backup instead and pick your last backup to restore back to your iPad.

Once the restore is complete, finish setting up the iPad and let it sync back to iTunes you can either cancel the sync, again or let it backup, again.

Then disconnect the iPad.

Do one hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

Once your iPad is back to the Home screen,

In the Settings App under the General tab, to the right under Spotlight sesrch, try disabling the search under apps that really do not need a search, like some games, remotes, apps that really do not need to be searched, etc., to reduce the list for Spotlight to search.

(optional for the 1st gen iPad Mini)

Try turning on Reduced Motion.

This is found in the Settings App in the General tab the left panel.

In the right panel look under Accessibility, the look for Reduce Motion and turn this feature "On".

You should see an appreciable performance increase on all iPad 2, 3 and 4 models.

(also, optional for the iPad Mini )

In the Settings App under the General Tab, in the right column, look for Background App Refresh and turn this setting to "off".

If you purchased any music from iTunes, you will need to redownload that content back to your iPad for playing directly from your iPad and not from Apple Music servers.

Also, if your iPad contained a lot of images in the Photos app, these will take time to regenerate the original AND thumbnail images themselves inside of the Photos app when you first launch it.

Good Luck!