Can android virus infects iOS by sharing hotspot?

In more detail...

Providing your iPad has been kept up-to-date with system software updates, you should not be overly concerned for your iPad being directly compromised by malware. Due to the sandboxed system architecture of iOS/iPadOS, unless jailbroken, your iPad is not susceptible to traditional malware infection per-se. However, as with all computer systems, there are still vulnerabilities and exploits to which you remain vulnerable. 

For older devices, no longer benefiting from regular security updates, the risk of an unpatched vulnerability being exploited increases. Regardless of the installed version of iPadOS, there are useful mitigations that can be used to significantly reduce your exposure to risk. For iPad, ensure that you have updated to the most recent version of iPadOS - the current version being iPadOS 18.3.2.

Be wary of an often repeated myth that Apple devices are immune to malware; those that perpetuate this fallacy, perhaps with good intention, do not necessarily comprehend the broader threat landscape. Apple expend considerable resources in developing and issuing regular software security updates and patches for its products; if the myth had any substance, regular security updates would be unnecessary.

The majority of threats to which you will be invariably exposed will surface via web pages or embedded links within email or other messaging platforms. Browser-based attacks can be largely and successfully mitigated by installing a good content and Ad-blocking product. One of the very best and most respected within the Apple App Store - designed for iPad, iPhone and Mac - is 1Blocker for Safari:

https://apps.apple.com/gb/app/1blocker-for-safari/id1365531024

1Blocker is highly configurable - and crucially does not rely upon an external proxy-service of dubious provenance, often utilised by so-called AntiVirus products intended for iOS/iPadOS. Instead, all processing by 1Blocker takes place on your device - and contrary to expectations, Safari will run faster and more efficiently.

Unwanted content is not simply filtered after download (a technique used by basic/inferior products), but instead undesirable embedded content is blocked from download. 1Blocker has also introduced its “Firewall” functions - that are explicitly designed to block “trackers”. Being implemented at the network-layer, this additional protection works across all Apps. Recent updates to 1Blocker has introduced additional network extensions, extending protection to other Apps.

A further measure to improve protection is to use a security focussed DNS Service in preference to automatic DNS settings. This can either be set on a per-device basis in Settings, or can be set-up on your home Router - and in so doing extends the benefit of this specific protection to other devices on your local network. I recommend using one of the following DNS services - for which IPv4 and IPv6 server addresses are listed:

Quad9 (recommended)

9.9.9.9

149.112.112.112

2620:fe::fe

2620:fe::9

OpenDNS

208.67.222.222

208.67.220.220

2620:0:ccc::2

2620:0:ccd::2

Cloudflare

1.1.1.1

1.0.0.1

2606:4700:4700::1111

2606:4700:4700::1001

Security focused DNS providers intentionally "sink hole" known bad or malicious websites and resources - this providing an additional layer of protection beyond that provided by your device and its Operating System. These DNS services will, when used alongside 1Blocker or other reputable Content Blocker, provide defence in depth.

There are advanced techniques to further “harden” iOS/iPadOS (such as using DoH, DoT and DNSSEC). Apple has recently introduced its new Private Relay to its iCloud+ subscribers - in part employing ODoH (a variant of DoH) as an element of this new functionality. DoH and DoT are now natively supported by iOS/iPadOS, however these protocols are only surfaced through adding a management profile to the device; this is easily implemented through using a third-party App such as DNSecure:

https://apps.apple.com/gb/app/dnsecure/id1533413232

Due to the system architecture of iOS/iPadOS, unless jailbroken, your iPad is not susceptible to traditional malware infection per-se, a "virus" being just one type of malware. However, as with all computer systems, there are still vulnerabilities and exploits to which you remain vulnerable. For older devices, no longer benefiting from regular security updates, the risk of an unpatched vulnerability being exploited significantly increases. 

While your iPad is unlikely to be directly infected by installable malware, your iPad can become a repository for infected files. While a locally saved file may not pose an immediate threat to your iPad (or iPhone), the file can still infect other susceptible devices (e.g., Windows PCs) if transferred to them.

In summary of threat to your iPad, malware is unlikely to be a concern for iOS/iPadOS devices that are kept updated to the most recent version of their operating system. That said, all computers have vulnerabilities and exploits, but iOS/iPadOS are perhaps less likely to be materially affected.

Continued...

no, ios devices can't run android software ( a virus would like an app qualify as android software)

only way to install new software, apps or vira or malware on an ios device is to use apple app store, you can't install software from mails, websites or sms links or by using wifi or anything like that.

and would suppose apple spend some resources on making sure their app store is vira free

the biggest threat to the security of your ios device is ironically enough you the user.

read

these are the ways to compromise your device read them carefully

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

and

If you think your Apple Account has been compromised - Apple Support

You're very welcome.

iPadOS 17.x remains supported for security updates at this time - and should continue to do so for at least the next eighteen months or so. While you should have no immediate concern for ongoing availability of security updates, you might be well advised to start thinking about replacement of your iPad with a newer model.