App reject my app with Guideline 5.2.5 - Legal - Intellectual Property, what's wrong?

The title and subtitle fields are marketing material. This means that you are using Apple trademarks in your marketing material. Trademarks are intellectual property. In a legal sense, you are stealing from Apple. Furthermore, property owners have a legal obligation to defend their property. Companies who don't do that have lost ownership of trademarks. The fact that you have improperly used Apple's trademarks in the past has no bearing. Apple has discovered this infringement and informed you. It is now your responsibility to respect Apple's trademark and remove it from both your new app and your existing ones.
Otherwise, what would stop some other company from using your app or company name in their own marketing materials?

Hi, if you read Guidelines for Using Apple's Trademarks and Copyrights you can see next:

"2. Compatibility: Developers may use Apple, Macintosh, iMac, or any other Apple word mark (but not the Apple Logo or other Apple-owned graphic symbol/logo) in a referential phrase on packaging or promotional/advertising materials to describe that the third party product is compatible with the referenced Apple product or technology, provided they comply with the following requirements.

b. The Apple word mark is used in a referential phrase such as “runs on,” “for use with,” “for,” or “compatible with.”"

I think this means that any developer can use words "for iMessage", "for iPhone" etc.

Take it up with App Review.

"2. Compatablility.....in a referential phrase" does not mean 'in the subtitle'. By incorporating the trademarked "iMessage" in your subtitle you have overstepped what Apple is allowing. The concern is that the purchaser of your app might confuse your product with Apple's iMessage product. That's the essence of a trademarked product.

"P.S. I already have another few stickers pack successfully approved, where in title/subtitle have "for iMessage" text. I don't understand why it's reject this time"

What you don't understand is why they didn't reject it before.

I don't know why, but for review team if title include "emojis for iMessage" it's reject with reason "iMessage in the app name or subtitle in an inappropriate manner"

But when I changed "emojis for iMessage" to "stickers for iMessage" it was approved.

I don't know whats wrong with word "emojis"

App Review is often inconsistent and sometimes overlooks things. You got luck. But next time you may not.