Is iOS 9.3.5 or 6 still available for iPad 2 to download?

No.

But you will never retrieve old third party apps from the iOS App Store, ever again, making this iPad a pretty much useless device.

Virtually all third party app developers have abandoned their older apps for older iOS devices running iOS 10 and earlier.

There is no way to retrieve any older apps from the iOS App Store, any longer and no more compatible apps, either.

These old 8 and 9-year old iPads are obsolete.

Sorry.

If you have already updated your iPad2 to iOS 9.3.5 (for WiFi Only models) or iOS 9.3.6 (Cellular+WiFi), a factory reset will not erase the installed version of iOS. An update, once installed cannot be updated; it is not possible to restore an earlier version.

Be advised that all 32-bit Apps that are compatible with iPad2 have long since been withdrawn from the Apple App Store. If you factory restore or fully reset your iPad, any downloaded Apps will be permanently lost. Once Apps are withdrawn from the App Store, they cannot be (re)downloaded or reinstalled. This may significantly impact the ongoing usability and usefulness of your iPad.

You may also experience difficulties re-activating your iPad. Given the age of your [now obsolete] iPad2, Apple Support are unlikely to offer assistance with reactivation of your iPad2.

Safari (and other Web Browsers installed on your iPad) is reliant upon the WebKit libraries - these also being an integral element of iOS. Whilst many websites will continue to render as expected, you may find that some websites won’t work properly with very old versions of WebKit and/or installed Web browsers.

You really do need to consider replacement of the your obsolete iPad2.

Also, that iOS 9.3 version of Safari is over 4-years old now and should be considered to be NOT secure for use on the Internet as that version of iOS Safari has NOT received ANY updates in over 4-years.

The version of the Safari Web browser should be consider an unfit app and NOT safe or secure to use to access the Intenet.

If you insist on using this very old iPad, a singular, NEW paid third party Web browser was introduced by a lone developer, during the pandemic, specifically for use with both very old and very new iPad models and has been consistently receiving regular updates from its lone developer.

This third party Web browser IS THE ONLY Web browser app left to still supoort iOS 9 and later.

This iOS 9/10 supported Web browser is called ALook Web browser.

ALook Web browser

https://apps.apple.com/us/app/alook-browser-2x-speed/id1261944766

If you are intent on still using this over 9-year old iPad, then pay for and download/install this Web browser before its developer decides to stop developing it for older iOS 9 and 10 devices!

This is THE ONLY THIRD PARTY WEB BROWSER that is still supporting older iPads still runnung iOS 9 and 10.

Best of Luck to You!