i have ipad mini 2, ios 9.3.5. now many app not support, can i upgrade ios upper 10

Are you sure that you have an iPad mini2 - and not, as is perhaps more likely, a first generation iPad mini? These two models are frequently misidentified. The information that you have provide suggests that you have an iPad mini1.

Not sure which iPad you have? Identify your iPad model.

An iPad mini1 can only be updated to iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular models).

Apple ended update support for the iPad mini1 in September 2016. This iPad cannot be updated to iOS 10 or later major versions of iOS, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS. This limitation cannot be bypassed; the mini1 is a 32-bit architecture device, whilst more recent versions of iOS/iPadOS are designed for 64-bit hardware platforms. The iPad mini1 is obsolete.

If you do indeed have an iPad mini2, this is capable of update to iOS 12.5.4 - with major update support having ended in September 2019.

Compatible Apps for your iPad are increasingly difficult to find - as third-party developers are increasingly dropping support for older versions of iOS preceding iOS11/12/13. As older versions of Apps are removed from the Apple App Store, you’ll not be able to (re)download or install them - which may severely limit the usefulness and utility of your iPad. As such, if you want or need to access most current Apps, requiring more recent versions of iOS, you’ll need to consider replacement of your iPad with a newer or current model.

Of current models, even the entry-level iPad8 has specifications and capabilities that will massively outperform you current iPad - and is compatible with the vast majority of current Apps. Other models are more powerful still.

I hope this information provides helpful and succinct clarity as to your available options - and the limitations of your current iPad.

It is possible you actually have/own a 2012, 1sr gen iPad Mini and NOT a 2013, 2nd gen iPad Mini.

Especially,if it is stuck on iOS 9.3.5.

Also, it won't matter if your iPad Mini could upgrade to iOS 10, either, which it can’t.

That iPad model may never upgrade beyond iOS 9.3.5.

That iPad Mini model is, at least, 8-years old, possibly 9-years old.

It is too old today.

Sorry.

Apple ended support for all 8-10-year old iOS devices well over 4 years, ago, in 2016.

Third party app developers abandoned and stopped supporting these 8-10-year old iOS devices nearly 3 years, ago, in 2018.

There are, virtually, NO MORE third party apps available from the iOS App Store, any longer!

Third party compatible apps for such old devices are few and far between, now, in 2021.

This includes apps for both iOS 9 AND iOS 10 devices!

It’s 2021, now.

If you need/want an iPad with an up to date iPadOS with access to current, updated apps, then you really need to seriously consider a purchase of a new iPad model OR a much, MUCH “newer” and less expensive, refurbished or used iPad models, from better known, trusted Apple product/device retailers/resellers, some locally or from online, on the Web/Internet, capable of running the latest iPadOS versions.

There are PLENTY of less expensive, newer, older iPad models that can run the latest, current versions of iPadOS.

I am sorry that you had to learn all of this, but this does not change any of the facts regarding these very old iOS devices.

Sorry & Best of Luck to You!